Treaties

Malgosia Fitzmaurice

Content type: Product: Max Planck

Encyclopedia Entries Encyclopedia of Public
Article last updated: International Law [MPEPIL]
February 2010

Subject(s):
Continental shelf — UNCLOS (UN Convention on the Law of the Sea) — Customary international law —
Lex specialis — Unilateral acts — Codification — Travaux préparatoires — Treaties, application —
Treaties, interpretation — Treaties, entry into force — Treaties, ratification — Treaties, binding force —
Treaties, invalidity, termination, suspension, withdrawal — Vienna Convention on the Law of Treaties —
Treaties, reservations and declarations
Published under the auspices of the Max Planck Foundation for International Peace and the Rule of Law
under the direction of Rüdiger Wolfrum.

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 A. Introduction
1 International law relating to treaties has largely been codified in the Vienna Convention on the
Law of Treaties (1969) (‘VCLT’). For the purposes of the VCLT, a ‘treaty’ is defined as ‘an
international agreement concluded between States in written form and governed by international
law, whether embodied in a single instrument or in two or more related instruments and whatever its
particular designation’ (Art. 2(1)(a); see paras 16–19 below).

2 The present article is principally concerned with the law of treaties within the confines of the
VCLT, taking also into account the relevant rules of customary international law. Treaties need to
be regarded in a wider context; they constitute the major mechanism for the development of legally
binding norms among States. To the extent such norms become binding on the national level or
determine the content of national law their legitimacy has been put into question (International Law
and Domestic (Municipal) Law).

3 An agreement between a State and a non-State entity does not constitute an international treaty,
although such an agreement may be governed by international law and may regulate international
law issues (see para. 19below).

B. Scope and Development of Treaties

1. Formal Requirements
4 The concept of a treaty in general international law is, in fact, broader than the definition of a
treaty for the purposes of the VCLT, and includes treaties between States and international
organizations (see para. 13below). The concept of an ‘international treaty’ is also wider than the
VCLT definition of a treaty, as it includes oral agreements which, though extremely rare between
States, are recognized as binding under the rules of customary international law.

5 Within the terms of the 1969 VCLT, treaties may take an infinite number of forms, from the most
elaborately drafted, and formally executed document, to a mere exchange of notes. A broad
concept of the definition of treaties was already advocated by the International Law Commission
(ILC), which, when defining the notion, stated that an agreement concluded by exchange of notes,
exchange of letters, agreed minutes, joint declarations, or other instrument may constitute a treaty
(UN ILC ‘Report of the International Law Commission to the General Assembly Covering the Work of
its Fourteenth Session’ [24 April–29 June 1962] [1962] vol II UNYBILC 157, 161). This view is also
reflected in international jurisprudence. The International Court of Justice (ICJ) in the South West
Africa/Namibia (Advisory Opinions and Judgments) (South-West Africa Cases [Ethiopia v South
Africa; Liberia v South Africa] [Preliminary Objections] [1962] ICJ Rep 319) stated ‘terminology is
not a determinant factor as to the character of an international agreement or undertaking’ (at 331).
In Aegean Sea Continental Shelf Case (‘Aegean Sea Case’) it affirmed that ‘it knows of no rule of
international law which might preclude a joint communiqué from constituting an international
agreement’ (at 39). In the 1994 Maritime Delimitation and Territorial Questions between Qatar and
Bahrain (Qatar v Bahrain) (‘Case between Qatar and Bahrain: 1994’) the ICJ considered the value
of minutes as an international agreement in the light of Art. 2(1)(a) VCLT and concluded that
minutes ‘constitute an international agreement creating rights and obligations for the Parties’ (at
122). Treaties may be bilateral, between two States only, or multilateral, between three or more
States including the so-called ‘universal treaties’ to which, at least as a matter of aspiration, all
States are intended to be parties (see paras 22–28 below).

2. Sources of International Law and Treaties

6 Treaties are listed as one of the sources in Art. 38(1) Statute of the International Court of Justice
([adopted 26 June 1945, entered into force 24 October 1945] 145 BSP 832; ‘ICJ Statute’) next to

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 customary international law and the general principles of law (Sources of International Law). Art.
38(1) ICJ Statue does not stipulate a hierarchy between treaty law, customary international law, and
the general principles of law. It is possible that the same matter is governed by a treaty and by
customary international law and that these rules coexist. In general, when there exists more than
one applicable rule, the choice between them is to be made by recourse to established principles
of interpretation such as by applying the maxims lex specialis derogat legi generali and lex
posterior derogat legi priori (UN ILC ‘Fragmentation of International Law: Difficulties Arising from the
Diversification and Expansion of International Law’ (2006) GAOR 61st Session Supp 10, 400, at
408–18 ; Interpretation in International Law). It will normally be the case that the treaty is the lex
specialis rule and prevails over inconsistent customary international law. The situation may be
different if a new norm of customary international law arises after the conclusion of the treaty. Then
the question may arise of whether custom overrides the treaty.

7 Besides the sources mentioned in Art. 38(1) ICJ Statute, there are other sources of international
law, such as decisions of international organizations or unilateral acts (Unilateral Acts of States in
International Law).

3. Normative Treaties, Traités-Lois, and Traités-Contrats

8 Regarding the content of treaties, a distinction is sometimes made between so-called ‘law-
making’ or ‘normative’ treaties and ‘contract’ or ‘reciprocal’ or ‘synallagmatic’ treaties (at one time
these two categories of treaty were frequently referred to, respectively, as traités-lois and traités-
contrats). Normative or contractual treaties are considered to further community interests by
setting up international standards which are best achieved by universal participation and are not
based on the principle of reciprocity. These standards have been described by ILC Special
Rapporteur Pellet as being created, above all, to institute common international regulation on the
basis of shared values (UN ILC ‘Report of the International Law Commission Covering the Work of its
Forty-Eighth Session’ [6 May–26 July 1996] GAOR 51st Session Supp 10, 81). They constitute a
divergent category, consisting of conventions codifying private international law, International
Labour Organization (ILO) conventions, treaties on the law of armed conflict, trade and the
environment, and human rights treaties. Contractual or reciprocal treaties, on the other hand, are
seen to further the individual interests of the participating States, aiming at their mutual benefit
which is best achieved through reciprocal obligations (do ut des). However, Pellet and the ILC
observed that treaties are rarely entirely normative or entirely synallagmatic (reciprocal) (UN ILC
‘Report of the International Law Commission Covering the Work of its Forty-Ninth Session’ [12 May–
18 July 1997] GAOR 52nd Session Supp 10, 47). In most cases, including human rights treaties,
they contain both contractual clauses providing for reciprocal rights and obligations as well as
‘normative’ clauses. The term ‘normative treaty’ is therefore generally used to refer to one in which
the provisions of a normative character dominate.

4. The Historic Development of Treaties

9 Since ancient times, political entities have used treaties as a tool to shape their international or
neighbourly relations. First examples of such instruments go back to the third millennium BC. In
antiquity, law and religion were closely related, belonging to the same domain of morals. For
example, religious elements were present in the ceremony relating to the conclusion of treaties. An
oath was sworn at the conclusion of treaties. As a consequence, God(s) witnessed the legal
undertakings and their performance so that a breach thereof would result in a religious sanction.
Historically, the most important role was fulfilled by peace treaties. They originated many basic
principles, which were later refined by States through general treaty practice.

10 An important step in the historical development of treaties has been the emergence of
multilateral treaties. At first, multilateral agreements were concluded in the form of a set of bilateral
treaties without any express link between them. The Peace of Westphalia is an example of this and

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 is considered the prototype of the first multilateral treaty (Westphalia, Peace of [1648]). The first
multilateral agreement in the form of a single instrument was the Final Act of the Vienna Congress
(1815) which summarized the transactions of the Congress (Acte du Congrès de Vienne, signé le 9
Juin 1815 in GF de Martens [ed] Supplément au Receuil des Principaux Traités d’Alliance, de Paix,
de Trêves, de Neutralité, de Commerce, de Limites, d’Échange etc. [Librairie de Dieterich Gottingue
1818] vol 6, 379).

5. Codifications of the Law of Treaties

11 The codification of the law of treaties started in the 20th century (Codification and Progressive
Development of International Law). In 1928 the American States adopted the Havana Convention
on the Law of Treaties (International Conference of American States ‘Convention on Treaties’
[1935] 29 AJIL Supp 1205). In 1935 the Harvard Draft Convention on the Law of Treaties (Harvard
Law School ‘Draft Convention on the Law of Treaties’ [1935] 29 AJIL Supp 653) was published as
part of the ‘Harvard Research in International Law’. After World War II the process of codification
was continued on a more formal basis by the ILC, whose work was consummated in the major
codifications of the Vienna Conventions (Vienna Convention on the Law of Treaties [‘VCLT’];
Vienna Convention on the Law of Treaties between States and International Organizations or
between International Organizations [‘VCLT-IO’]; Vienna Convention on Succession of States in
Respect of Treaties [‘VCSS-T’]).

(a) The 1969 Vienna Convention on the Law of Treaties (VCLT)

12 The VCLT was the result of the work of the ILC and of the 1968 and 1969 United Nations (UN)
Conference on the Law of Treaties. It entered into force on 27 January 1980. The VCLT has been
taken to reflect, in general, customary international law in its substantive provisions, although, at
the time of its entry into force, some doubts were raised as to the customary international law
status of some of its provisions, such as Arts 34–38 (treaties and third States) and Arts 65–68
(procedure in case of alleged invalidity or suspension of treaties), which probably still do not
represent customary international law. Art. 73 VCLT states that its ‘provisions…shall not prejudge
any question that may arise in regard to a treaty arising from a succession of States or from the
international responsibility of a State or from the outbreak of hostilities between States’, issues
which were left outside its scope.

(b) The 1978 and 1986 Vienna Conventions (‘VCSS-T’ and ‘VCLT-IO’)
13 There are two further Vienna Conventions which relate to the law of treaties: the 1978 VCSS-T
on the succession of States in respect to treaties and the 1986 VCLT-IO, which deals with treaties
between States and international organizations or between international organizations themselves.
The VCLT-IO adapts the rules of the VCLT to treaty relations concerning international organizations.
The VCSS-T is in force, though not all of its provisions are considered to represent customary
international law. The VCLT-IO, on the other hand, has not entered into force, though its rules are
generally considered to constitute customary international law.

6. Extent of the Binding Force of Treaties

14 The general rule under the law relating to treaties, whether bilateral, contractual, or reciprocal,
treaties or multilateral normative treaties, is that they are legally binding for their parties. They are
binding, however, only for their parties. There are limited exceptions to this general principle (see
paras 97–101 below). Apart from that, treaties which are the constitutive instrument of an
international organization can be seen as implying a special normative relevance in relation to non-
member States in that the organization may have an objective international legal personality
(Obligations erga omnes), as indicated in 1949 by the ICJ in Reparation for Injuries Suffered in the
Service of the United Nations (Advisory Opinion) ([1949] ICJ Rep 174).

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 15 Treaties may also extend their normative relevance beyond their actual parties and the scope
of their operation through the influence they may have on the development of new rules of
customary international law through State practice (including the practice of non-parties to a
treaty). In the North Sea Continental Shelf Cases (Federal Republic of Germany/Denmark; Federal
Republic of Germany/Netherlands) ([1969] ICJ Rep 3), the ICJ illustrated the conditions under which
such a process may take place. The ICJ observed, first, that the provision concerned should be of
a fundamentally norm-creating character, such as could be regarded as forming the basis of a
general rule of law; and, secondly, that a very widespread and representative participation in the
convention might suffice of itself, provided it included those States whose interests were
specifically affected, even without the passage of any considerable period of time. The ICJ further
explained the relationship between customary international law and the law of treaties in the 1986
Military and Paramilitary Activities in and against Nicaragua Case (Nicaragua v United States of
America) (‘Nicaragua Case’) in which it particularly focused on the parallel existence of treaty rules
and rules of customary international law with the same or similar obligations. In such cases, the ICJ
stated, the treaty continues to operate as between the parties to it, while the parallel relations
between non-parties, or between non-parties and parties, are governed by the corresponding
customary international law.

C. The Legal Nature of Treaties

1. What Constitutes a Treaty Under International Law?

(a) Description
16 A treaty may be described in a multitude of ways, as was stated by the ILC. The names such as
‘convention’, ‘protocol’, ‘charter’, ‘pact’, ‘agreement’, ‘concordat’, or ‘joint communiqué’ may be
used.

(b) Legally Binding/Intention to be Bound

17 Each treaty has to be separately assessed to ascertain whether it constitutes a binding
agreement or not. According to the jurisprudence of the ICJ the legal character of an agreement
has to be decided on the basis of an objective analysis of the text rather than on the subjective
intention of the parties. The ICJ has held that an instrument, in order to constitute a binding treaty,
must enumerate commitments to which the parties have consented in order to create rights and
obligations in international law for the parties (Case between Qatar and Bahrain: 1994 121). The ICJ
also determined that the nature of the transaction, the text, and the circumstances of its conclusion
must be taken into consideration. (Aegean Sea Case 39; Case between Qatar and Bahrain: 1994
121; Land and Maritime Boundary between Cameroon and Nigeria Case [Cameroon v Nigeria] 431).

(c) Governed by International Law

18 The term ‘governed by international law’ forms a part of the definition of a treaty contained in
Art. 2(1)(a) VCLT. This is aimed at the exclusion from the definition of those agreements which,
although with the participation of a State or States, are governed by a law other than international.

19 There are groups of agreements which, although concluded by subjects of international law,
fall under national law—such as the purchase of property by a State. Another group are
agreements between States and a foreign natural or legal private law person (Contracts between
States and Foreign Private Law Persons), such as concession agreements, the character of which
is not entirely clear. One view is that such an agreement can be a treaty governed by international
law, if the parties so intended, and the opposite view maintains that the conditio sine qua non of an
international treaty is the existence of at least two parties who are subjects of international law. The
ICJ in the 1952 Anglo-Iranian Oil Company Case, adhered to the view that a concession agreement

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 between the United Kingdom and the Iranian Oil Company was a private contract (at 112).

2. Non-binding Agreements
20 States have always, in the course of their normal diplomatic or political relations, entered into
non-binding arrangements (or informal agreements), frequently referred to as memoranda of
understanding or modus vivendi.

21 More recently, in particular in the fields of international economic law, human rights law, and
international environmental law, it has become a practice for States to enter into arrangements, or
make extensive formal declarations, which are not intended to be legally binding on them, though
they may be intended to create political or moral pressure on the participating parties to act in
accordance with their provisions. These arrangements are often referred to as soft law. It may
often be difficult to distinguish between treaties and such so-called soft law instruments (eg codes
of conduct), which may assume a form similar to an international agreement (see eg Food and
Agriculture Organization of the United Nations ‘Code of Conduct for Responsible Fisheries’ [adopted
31 October 1995]).

3. Categories of Treaties

(a) General Rule

22 The VCLT does not introduce any differentiation of treaties. A few articles of the VCLT refer to
certain categories of treaties, such as Art. 62(2)(a) relating to treaties establishing a boundary and
Art. 5 relating to treaties which are a constituent instrument of an international organization.

23 A number of categorizations or distinctions among treaties have, however, been suggested by

academic or practicing lawyers, on the basis of the purposes for which treaties exist, or of certain
effects which they may have. Such categorizations are merely for convenience of grouping certain
types of treaty with respect to which common practices or contents are in the course of being
developed (eg the so-called Multilateral Environmental Agreements [‘MEAs’]; Environment,
Multilateral Agreements). International environmental law in particular has established a creative
manner of international treaty-making through the use of so-called ‘framework’ and ‘umbrella’
conventions, which stipulate general rights and obligations of the parties (Framework Agreements).
A more concrete catalogue of rights and obligations, as well as new developments in the areas
covered by the framework and umbrella conventions, is supplemented by protocols or other
agreements. These are, in fact, independent international treaties (such as the Vienna Convention
for the Protection of the Ozone Layer [adopted 22 March 1985, entered into force 22 September
1988] 1513 UNTS 324; ‘VCPOL’) and the Montreal Protocol on Substances that Deplete the Ozone
Layer ([adopted 16 September 1987, entered into force 1 January 1989] 1522 UNTS 3; ‘Montreal
Protocol’). Appendices or Annexes may also supplement such framework agreements (consider,
for example, the International Convention for the Prevention of Pollution from Ships, 1973 [signed 2
November 1973, entered into force 2 October 1983] 1340 UNTS 184 [MARPOL Convention] which is
supplemented by six Annexes).

(b) Categorization by Subject-Matter

24 According to their subject-matter there are numerous types of agreements: such as peace
treaties, military alliances, cultural agreements, arbitration and conciliation treaties, guarantee
treaties, and concordats. A concordat is an agreement concluded between the Holy See and a
State regulating the legal position of the Church in that State or on matters of immediate relevance
to the Catholic Church as such. An example of a concordat between the Holy See and a federal
state of the Federal Republic of Germany (‘Germany’) is the ‘Konkordat zwischen dem Heiligen
Stuhl und dem Lande Niedersachsen’ ([done 26 February 1965] [1965] 57 Acta Apostolicae Sedis

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 834).

(c) Multilateral/Bilateral
25 Treaties can be bilateral or multilateral. Treaties which aspire to attract universal participation
are generally called ‘universal treaties’, perhaps the most important example being the United
Nations Charter. But there are many other treaties which aspire to universal participation, and a
number which have come close, at least, to achieving it—such as the Convention on International
Trade in Endangered Species of Wild Fauna and Flora ([opened for signature 3 March 1973,
entered into force 1 July 1975] 993 UNTS 243), and the Convention on the Rights of the Child
([adopted 20 November 1989, entered into force 2 September 1990] 1577 UNTS 3), which has
been ratified by every country except the United States and Somalia. Other examples are to be
found in the major MEAs. For instance, both the VCPOL and the Montreal Protocol, as well as the UN
Framework Convention on Climate Change (with Annexes) ([adopted 9 May 1992, entered into
force 21 March 1994] 1771 UNTS 107) and its Kyoto Protocol ([adopted 10 December 1997,
entered into force 16 February 2005] [1998] 37 ILM 32), aspired to universal participation. But,
while the VCPOL and the Montreal Protocol were ratified by all but one country, the Kyoto Protocol
never actually achieved anything near universal ratification.

26 Treaties may be ‘open’ or ‘closed’. There are different categories of closed treaties: they can
enumerate or limit the number of States which can participate, or they may condition the
participation on unanimous acceptance of new members by signatory States. For example, the
1928 General Act for the Pacific Settlement of International Disputes ([concluded 26 September
1928, entered into force 16 August 1929] 93 LNTS 343) ‘is open…to accession by all the heads of
states or other competent authorities of the members of the League of Nations and the non-member
states to which the Council of the League of Nations has communicated a copy for this purpose’
(Art. 43(1)). There is also a category of treaties, which while less strict than ‘closed’ treaties in this
respect, are not entirely ‘open’ for the accession of any State. In these treaties, the acceptance of
a new member depends on a majority of signatory States voting in its favour. An example of such a
treaty is the 1974 Agreement on an International Energy Program (with Annex) ([concluded 18
November 1974, entered into force 19 January 1976] 1040 UNTS 271). ‘Open’ treaties also form a
very divergent category: they may be unconditionally open to all States; or may prescribe a
special admission procedure, such as Art. 4 UN Charter. Another example is the 1992 Convention
on the Protection of the Marine Environment of the Baltic Sea ([adopted 9 April 1992, entered into
force 17 January 2000] 2099 UNTS 195), which is ‘open for accession by any other State or
regional economic integration organization interested in fulfilling the aims and purposes of this
Convention, provided that this State or organization is invited by all the contracting parties’ (Art.
35).

27 The constituent instruments of international organizations are widely regarded as forming a

special category of treaties, in particular because of the special rules of interpretation that are held
to apply to them, involving both a more teleological approach to their interpretation than that
applied to other forms of treaty, as well as the special regard accorded to the practice developed
by their organs.

(d) Pactum de Contrahendo, Pactum de Negotiando

28 Finally, mention must be made of the notions of pactum de contrahendo, pactum de
negotiando. These concepts relate to obligations to reach an agreement and to negotiate with a
view of reaching an agreement. These obligations often arise from an existing treaty, which binds
the parties to negotiate and, as is the case in pactum de contrahendo, to enter into further
agreements. The content of the obligations is controversial, as are the consequences of not
reaching an agreement due to unsuccessful negotiations.

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 D. Formulation of Treaties

1. Introductory
29 States may adopt any procedure they choose to bring a legally binding agreement into
existence between them. However, in the absence of any other agreement, the elaborate
procedures set out in the VCLT apply; these procedures reflect the practice which had developed
between States before the codification of the law in the VCLT.

30 Broadly, this procedure may be divided into two parts. First comes the procedure of negotiation
and adoption of the text of a treaty (see paras 31–37 below), and secondly the formal procedure
whereby States express their consent to be bound by that text (see paras 52–55 below). This, it
may be observed here, generally but not invariably, involves a two-step procedure, consisting of
first, the signature of the treaty, and second, its ratification.

2. Treaty Negotiations and the Adoption of a Text

(a) Negotiation
31 The first stages in the formulation of a treaty consist of discussions and negotiations at which
the subject matter to be included in the treaty is agreed and a draft text is prepared. There is no
particular form prescribed for treaty negotiations, which can be oral, in written form, or both. In the
case of bilateral treaties, discussions and negotiations are generally initiated at the level of the
parties themselves, and can be conducted at different levels, by Heads of State[s] or
Governments, by Ministers of Foreign Affairs or, more often in diplomatic practice, at the level of
officials (Heads of Governments and Other Senior Officials).

32 The negotiation of multilateral treaties is often instigated not by States, but by international
organizations, such as the UN, International Maritime Organization (IMO), Food and Agriculture
Organization of the United Nations (FAO), ILO, or United Nations Educational, Scientific and Cultural
Organization (UNESCO). Many international treaties have been prepared by the ILC (such as the
VCLT).

33 Conferences have their own rules of procedure (Conferences and Congresses, International).
Art. 9 (2) VCLT gives a default rule according to which a convention may be normally adopted at
an international conference by a two-thirds majority. The classical rule was that of unanimity, which
proved to be a stumbling block in the adoption of multilateral treaties. The two-thirds majority rule,
however, may lead to not taking into account minority interests. An alternative practice has
developed according to which the text of a treaty can be adopted by consensus, ie without
resorting to a vote, and in the absence of a formal objection to follow this course of action. This has
a significant impact upon the format of conference deliberations.

34 The formal document summarizing the proceedings of a diplomatic conference and recording
its results is called a final act. It usually mentions the purpose of the conference, lists the
participating States, and includes the text of the adopted treaty as an attachment.

35 The negotiation of treaties at conferences involves great organizational and administrative

tasks which frequently are exercised by the secretariat of the organization sponsoring the
conference (International Organizations or Institutions, Secretariats). This includes enabling a
smooth running of the negotiations by providing for instant translation and interpretation services,
and the distribution of relevant documents. This may also include more substantial tasks such as
the preparation of background studies, or participation in drafting an initial negotiation text. It may
also take the form of influencing the topics on the agenda of meetings, advising on how to
negotiate difficult issues or facilitating the brokering of compromises and agreements. Sometimes,

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 secretariats, de facto, exercise a significant influence on the content of an international treaty.

(b) Adoption and Authentication of the Text

36 The processes of adoption and authentication of the text of a treaty may take any form agreed
by the parties (Arts 9, 10 VCLT). In the case of the text of a multilateral treaty adopted at a formal
diplomatic conference, this will generally be by way of the inclusion of the text in the final act of the
conference (see para. 35above).

37 The adoption and authentication of a text, whether by way of its incorporation in the final act of
a conference or by other means, may involve the signature, or initialling, either of the final act, or
of the text (see Arts 9, 10 VCLT). But such a signature is not to be confused with what may be a
second signature of the treaty for the purposes of signifying a State’s consent to be bound by it,
which is part of the second stage in the formation of a treaty covered in paras 52–55 below (and
governed by Art. 12 VCLT). Such a signature for authentication does not amount to an expression
of consent to be bound, nor does it commit a State to consider signing and/or ratifying the treaty. In
the interim period between the signature of an international treaty, a State is under the obligation
not to defeat the object and purpose of a treaty it has signed (see para. 48below).

3. Competence to Bind a State

38 One important issue in the conclusion of treaties, is the question of so-called ‘full powers’,
defined in Art. 2(1)(c) VCLT as a:

document emanating from the competent authority of a State designating a person or

persons to represent a State for negotiating, adopting or authenticating the text of a treaty,
for expressing the consent of the State to be bound by a treaty, or for accomplishing any
other act with a respect to a treaty.

Theholder of full powers is authorized to adopt and authenticate the text of a treaty and express
consent of the State to be bound by a treaty (Treaty-Making Power). There are a growing number of
treaties, in particular bilateral treaties, which do not require the production of full powers (eg
exchange of notes).

39 The general rule in Art. 7(1)(a) and (b) VCLT, is that a person is considered as representing a
State if he or she produces appropriate full powers or if it appears from the practice of the States
concerned, or from other circumstances, that their intention was to consider that person as
representing the State and to dispense with full powers. There is, however, a group of persons who
by virtue of their functions are considered to have such authority, these being: Heads of States,
Heads of Governments, and Ministers of Foreign Affairs, Heads of Diplomatic Missions (for the
purpose of the adoption of the text of a treaty between the accrediting State and the State to which
they are accredited); and representatives accredited by States to an international organization or
one of its organs (for the purpose of adopting the text of a treaty in that conference, organization,
or organ) (Art. 7(2) VCLT). Full powers have to be distinguished from credentials, which are
submitted to an international organization or a government hosting a conference by a delegate
attending to negotiate a multilateral treaty and to sign a Final Act. Signing a treaty itself requires full
powers or specific instructions from government.

40 When an unauthorized person purports to conclude a treaty, Art. 8 VCLT provides that the
action is without legal effect, unless subsequently confirmed by the State in question. On the other
hand, Art. 47 VCLT provides that where an authorized representative of a State expresses consent
to be bound, although instructed by a State not to do so, such a conduct does not invalidate this
consent, unless the limitation in his or her authority was notified to other negotiating States.

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 4. Expression of Consent to be Bound

(a) What is Meant by Consent to be Bound

41 A State’s ‘consent’ or ‘intention’ to be bound by a treaty cannot bring about the formation of a
legally binding agreement unless it is, ‘expressed’ in some external form.

(b) The Means of Expression of Consent to be Bound

42 According to Art. 11 VCLT, the ‘consent of a State to be bound by a treaty may be expressed
by signature, exchange of instruments constituting a treaty, ratification, acceptance, approval or
accession, or by any other means if so agreed’. There are no strict rules on the manner in which
consent to be bound may be expressed; parties to a treaty may decide this between themselves,
the matter generally being specified in the treaty itself.

43 Art. 2(1)(b) VCLT provides that ‘“ratification”, “acceptance”, “approval” and “accession”
mean in each case the international act so named whereby a State establishes on the international
plane its consent to be bound by a treaty’. In the case of ratification, it needs to be borne in mind
this is not the internal process of ratification (in States with democratic constitutions, generally by
way of act of the legislature), but an international act of the State, usually by way of signature by
the Head of State or Government, or by a Foreign Minister, of a document in the form of an act of
ratification.

44 There was a debate concerning the theoretical supremacy, in the absence of an agreement by
the parties, of signature or ratification as the decisive means of expressing consent to be bound.
This is not entirely settled, yet. In support of a requirement for ratification, in the absence of
agreement to the contrary, it may be noted that in 1924, Judge Moore stated in Mavrommatis
Palestine Concessions (Greece v Great Britain) (Jurisdiction) (Mavrommatis Concessions Cases)
that the view that treaties might be regarded as binding before they had been ratified was obsolete
(at 57).

45 Acceptance or approval of a treaty following signature, unless the treaty otherwise provides,
fulfil the same function as ratification following signature, and follow similar rules (Art. 14(2) VCLT).
The modes of expressing consent to be bound by acceptance and approval following signature
were introduced into treaty practice in order to accommodate different internal or constitutional law
procedures relating to the treaty-making process.

46 Accession (which is the act whereby a State accepts the offer or the opportunity to become a
party to a treaty already negotiated and signed by other States) is regulated by Art. 15 VCLT
according to which a State may accede to a treaty if it so provides, or if the parties agree.

(c) The Interim Stage between Signing and Ratification of a Treaty

47 The interim stage between the signing of a treaty and its ratification enables States to obtain
any necessary parliamentary approval and/or to enact required legislation. Signature of a treaty in
itself only expresses consent to be bound when it constitutes the final stage in the process of
making a particular treaty.

48 With regard to the interim obligation not to defeat a treaty’s object and purpose prior to its entry
into force (Treaties, Object and Purpose; Treaties, Provisional Application), codified in Art. 18 VCLT,
reference may be made to what has been termed the US’s ‘unsigning’ of the Rome Statute of the
International Criminal Court ([adopted 17 July 1998, entered into force 1 July 2002] 2187 UNTS 90
[‘Rome Statute’]) in 2002. This refers to the US’s letter informing the depository of the Rome Statute
of the US’s intention not to become a party to the treaty. While no withdrawal of signature actually
occurred, the interim obligation, to the extent that it exists under the customary international law of
treaties, was terminated with regard to the US, who are not a party to the VCLT.

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 (d) Entry into Force
49 Entry into force means that the treaty becomes binding upon the parties to it and acquires full
legal force as a legal act (Treaties, Conclusion and Entry into Force). Prior to the treaty’s entry into
force, some of its final clauses are already applicable (those referred to in Art. 24(4) VCLT).
Regarding multilateral treaties, a distinction can be made between the treaty’s general entry into
force and its entry into force for a particular State. The treaty’s general entry into force occurs
upon fulfilling the conditions prescribed in the treaty itself. After this general entry into force, the
treaty may enter into force for a particular State once such a State has expressed its consent to be
bound by the treaty.

50 Entry into force may be distinguished from entry into operation. Entry into force involves the
commencement of the legal obligation of the parties to perform in accordance with the provisions of
the treaty; entry into operation relates to the actual commencement of that performance.

51 Entry into force of a treaty may have legal effects within the domestic legal system of the
States party to it. States Parties may be under an obligation to modify the national legal system so
as to implement the international obligation. In principle, States have several options on how to
achieve this objective. They may do so either by altering the national law or by incorporating the
international agreement in question into their legal system. Occasionally international agreements
prescribe which actions on the national level are to be undertaken. For example, Art. 4 International
Convention on the Elimination of all Forms of Racial Discrimination ([opened for signature 7 March
1966, entered into force 4 January 1969] 660 UNTS 195) requires parties to suppress and punish
the incitement to racial hatred by declaring such acts as criminal offences. Most multilateral
environmental agreements require implementing national legislation or administrative actions.
Instances of such action include the setting up of systems to implement at domestic level the
emissions reductions required of developed States under the Kyoto Protocol, and the creation of
civil liability regimes, for instance in relation to oil pollution and nuclear accidents.

5. Consent to be Bound through ‘Conferences’, or ‘Meetings’, of the

Parties (COPs/MOPs)
52 A legally interesting phenomenon in recent years in relation to the question of consent to be
bound is the growing ‘legislative’ powers of conferences of the parties or meetings of the parties
(‘COPs’ or ‘MOPs’; Conference [Meeting] of States Parties) established by a number of modern
multilateral treaties, including matters of the law of the sea, in the human rights field, treaties in the
economic and health fields such as the WHO Framework Convention on Tobacco Control ([adopted
21 May 2003, entered into force 27 February 2005] 2302 UNTS 166), and some of the MEAs.

53 Some of these agreements set up organs such as the COPs/MOPs which are mandated to carry
out certain functions in relation to the implementation and operation of the treaty regime. This may,
but does not always, involve the use of so-called ‘enabling clauses’ which give a specific mandate
to such organs to elaborate in more detail rules in particular areas without providing for specific
amendment procedures.

54 One of the first examples of such provisions is the procedure for ‘adjustments and reductions
of production or consumption of the controlled substances’ provided in Art. 2(9) 1987 Montreal
Protocol. Another well-known example is the enabling clauses of the Kyoto Protocol (Arts 6, 12, 17)
whereby the COP/MOP is mandated to elaborate the rules and procedures of the extremely
important ‘flexible mechanisms’, including in particular the emissions trading system, which are
only covered in a very general sense in the Kyoto Protocol itself.

55 Thus, States Parties to certain multilateral treaties, by comparison to the traditional expression
of consent ex post facto (in relation to the content of the agreement) express their consent to be
bound ‘in advance’ and without prior full knowledge the content of the agreement. It may be said

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 that the precursor of such powers of the organs of international organizations can be found in the
system of the tacit agreement or in other words, the opting out system (Tacit Consent/Opting Out
Procedure). States have developed different mechanisms to nationally implement such ‘secondary
rules’ developed by meetings of States Parties.

6. Treaties, Reservations

(a) Nature of Reservations

56 The VCLT provides the following definition in Art. 2(1)(d):

‘reservation’ means a unilateral statement, however phrased or named, made by a State,

when signing, ratifying, accepting, approving or acceding to a treaty, whereby it purports
to exclude or to modify the legal effect of certain provisions of the treaty in their application
to that State.

57 Broadly, reservations are a means whereby the parties to a treaty may, individually, modify the
extent of their consent to the terms of the treaty. Generally, the issue of reservations is only
relevant in the context of multilateral treaties (Treaties, Multilateral, Reservations to). The right to
make reservations is part and parcel of a State’s expression of consent to be bound by the treaty,
in the sense that it should only be bound by precisely that to which it has consented. The corollary
of this is that other States cannot be obliged, against their will, to accept the reservation. It follows
that in relation to a multilateral treaty, where one or more parties make a reservation which some
parties accept and others do not, the effect of the reservations system is to give rise to a series of
differentiated obligations as between pairs of parties. In other words, reservations to a certain
extent ‘bilateralize’ the relations under a multilateral treaty.

(b) The Regime of the Vienna Convention

58 The modern approach which became the foundation of the reservations regime of the VCLT
was introduced by the ICJ in its 1951 Reservations to the Convention on the Prevention and
Punishment of the Crime of Genocide (Advisory Opinion) (Genocide Convention, Reservations
[Advisory Opinion]). The principal feature of this system was that:

a State which has made and maintained a reservation which has been objected to by one
or more of the parties to the Convention but not by others, can be regarded as being a
party to the Convention if the reservation is compatible with the object and purpose of the
Convention; otherwise, that State cannot be regarded as being a party to this Convention.
(At 29)

59 The VCLT reservations regime is characterized by its attempt to strike a balance between
‘integrity’ and ‘universality’, by which is meant the integrity (of the content) of a treaty and the
widest possible participation. Art. 19(c) VCLT aims at preserving the integrity of the core of the
treaty’s content in providing that a State may not submit a reservation, which is ‘incompatible with
the object and purpose of the treaty’. Art. 20(4)(b) VCLT tips the balance towards widening
participation by providing for treaty relations even between a reserving and an objecting State,
unless a contrary intention is expressed by the objecting State. Art. 20(5) VCLT provides that, in
general, a reservation is considered to have been accepted if it is not objected to within 12 months
of its notification. Finally, while reservations to treaty provisions which codify customary
international law are possible, reservations to provisions reflecting norms of ius cogens are not.

60 There are several unresolved issues in respect to reservations. First, the method for
determining the object and purpose of a treaty is far from uncontroversial. Secondly, the legal
consequences of a reservation being ‘impermissible’ due to its incompatibility with the treaty’s
object and purpose are contested. DW Bowett coined the terminology for the two schools of

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 thought which have emerged with regard to this problem: according to the school of ‘opposability’
(famous proponent eg JM Ruda), the permissibility of a reservation depends exclusively on its
acceptance by another State (it is suggested that its compatibility with the treaty’s object and
purpose could serve as a guideline for the State’s decision on whether or not to accept it);
according to the school of ‘impermissibility’ (famous proponent eg DW Bowett), a reservation is
invalid from its inception if it is impermissible due to its incompatibility with the treaty’s object and
purpose, and the acceptance by other parties will not repair it. In other words, only permissible
reservations can, in a second step, be accepted or, for other reasons than incompatibility with the
treaty’s object and purpose, be objected to. The question of so-called impermissible reservations
resulted in a discussion on the severability of such reservations from the State’s expression of
consent. This problem is particularly pertinent in relation to reservations to human rights treaties
(see eg the jurisprudence of the European Court of Human Rights [ECtHR] in relation to
reservations to the European Convention for the Protection of Human Rights and Fundamental
Freedoms [(signed 4 November 1950, entered into force 3 September 1953) 213 UNTS 221]).

(c) Further Developments

61 In 1993 the unresolved issues in the reservations regime of the VCLT prompted the ILC to
undertake a topic entitled ‘The Law and Practice Relating to Reservations to Treaties’, on which
Professor A Pellet was appointed as Special Rapporteur. Six major problems of substance
predominated in the discussion within the ILC that followed Pellet’s first report: the definition of
reservations; the distinction between them and interpretative declarations (see para. 62below), and
the differences of their legal regime which characterize the two legal institutions; the doctrinal
dispute between the ‘permissibility’ and ‘opposability’ schools; the settlement of disputes; the
effects of succession of States on reservations; and the question of the unity or diversity of the
legal regime applicable to reservations.

(d) Interpretative Declarations

62 States may also append ‘interpretative declarations’ to treaties when expressing their consent
to be bound (Treaties, Declarations of Interpretation). Such declarations are not addressed in the
VCLT. As opposed to reservations, mere interpretative declarations are explanatory in character
and set out how a State perceives its treaty obligations. In practice it may be difficult to draw the
line between ‘mere interpretative declarations’ and ‘reservations’. In the event that so-called
interpretative declarations aim at changing the scope of the obligation, they cease to be
declarations and become reservations, as a result of which States may treat them as reservations
(so-called ‘qualified interpretative reservations’) (see eg Belilos v Switzerland [ECtHR] Series A No
132).

7. Invalidity of Treaties

(a) The Right to Impeach the Validity of a Treaty

63 According to Art. 42(1) VCLT the validity of a treaty or of the consent of a State to be bound by
a treaty may be impeached only through the application of the VCLT (Treaties, Validity). The
invalidity or termination in whatever form of a treaty under the VCLT itself does not impair the duty
of any State to fulfil any obligations embodied in the treaty to which it would be subject under
international law independently of the treaty (Art. 43 VCLT; Treaties, Termination). A State may lose
a right to invoke a ground for invalidating or terminating a treaty if, after becoming aware of the
facts, it asserts or acquiesces in the treaty’s validity either by express agreement or through its
conduct (Art. 45 VCLT).

(b) Grounds for Invalidity

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 64 Generally, the grounds for invalidity of treaties within the VCLT can be divided into two groups:
relative grounds in Arts 46 to 50; and absolute grounds in Arts 51 to 53. The main difference
between these grounds is that the establishment of an absolute ground means that the treaty has
no legal force, whilst the establishment of a relative ground means that the consent of a particular
State to a multilateral treaty is invalidated (Art. 69(4) VCLT). This will not cause the treaty as a
whole to be void and the treaty will remain valid as between the remaining parties. However, the
treaty relations between the State whose consent has been invalidated and the other States are
void. With regard to bilateral treaties, the establishment of relative and absolute grounds have an
identical effect, they both render the treaty void.

65 Art. 46 VCLT deals with the failure to comply with internal law regarding competence to
conclude a treaty, and provides that this may be a ground for invalidating the treaty, if that failure
was ‘manifest’. Art. 47 VCLT concerns the situation in which the representative purporting to
conclude the treaty were acting ultra vires. Art. 48 VCLT addresses the effect of error in relation to
consent to be bound by a treaty (see the 1962 Temple of Preah Vihear Case). Arts 49 and 50 VCLT
deal with fraud and corruption. The coercion of a representative (Art. 51 VCLT) and coercion of a
State (Art. 52 VCLT) and conflict with the norm ius cogens (Art. 53 VCLT) are absolute grounds for
invalidity of a treaty. The consequences of such invalidity are regulated by Art. 71 VCLT.

(c) International Law’s Tendency in Favour of Stability and Validity

66 As a general proposition, it can be said that international law favours the stability of treaty
relations, for instance see Art. 62 VCLT. Thus the ICJ in the 1997 Gabčíkovo-Nagymaros Case
(Hungary/Slovakia) observed that the stability of treaty relations implies that the plea of
fundamental change of circumstances should be applied only in exceptional circumstances (at 65;
Treaties, Fundamental Change of Circumstances).

67 In the same case the ICJ took the view that the violation of treaty rules or of rules of general
international law may justify the adoption of certain measures, including countermeasures by an
injured State but it does not constitute a ground for termination under the law of treaties (ibid 65).

8. Treaties, Revision, Amendment, and Modification

68 In the VCLT, the term ‘amendment’ refers to changes to the treaty as between all the parties,
whereas ‘modification’ relates to changes between certain of the parties only (inter se), a
distinction which is only relevant in the context of multilateral treaties (Arts. 39–41; Treaties,
Amendment and Revision). The VCLT does not use the term ‘revision’ of treaties, based on the
ILC’s perception that certain ‘nuances’ had become attached to it in the period preceding World
War II (Commentary to Art. 35, UN ILC ‘Draft Articles on the Law of Treaties with Commentaries’
[1966] GAOR 21st Session Supp 9, 20). Nevertheless, the term is still used in practice, and the
distinction between the procedures of ‘amendment’ and ‘revision’ is not clear-cut. Broadly, two
views can be distinguished in the practice of the law of treaties. According to one, revision
basically means amendment. According to the other, revision is a more comprehensive process
resulting in changes to the treaty as a whole, as opposed to changes to specific provisions of a
treaty. Support for this view can be found in treaties which regulate both their amendment as well
as their revision, such as the UN Charter (Arts 108, 109 respectively), or the 1974 Convention on
the Protection of the Marine Environment of the Baltic Sea (Arts 23, 22 respectively), but, as
indicated above, this use of terms is not consistent in State practice.

69 The default rule in the VCLT provides that a treaty can be amended by agreement between the
‘parties’. Art. 2(1)(g) VCLT implies that the treaty, which is to be amended, has already entered into
force. In practice, however, there are examples of treaties which have been amended prior to their
entry into force. The most famous example of these is probably the United Nations Convention on
the Law of the Sea ([concluded 10 December 1982, entered into force 16 November 1994] 1833

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 UNTS 397), Part XI of which was not only ‘implemented’ but in effect amended by the so-called
‘1994 Implementation Agreement’ (Agreement Relating to the Implementation of Part XI of the United
Nations Convention on the Law of the Sea of 10 December 1982 [done 28 July 1994, entered into
force 28 July 1996] 1836 UNTS 41; Implementation Agreements).

70 Furthermore, a treaty may be amended through the subsequent and uniform practice of all its
parties. A well-known example of this relates to Art. 27(3) UN Charter, which concerns voting in the
UN Security Council. Despite the terminology of an ‘affirmative vote of nine members including the
concurring votes of the permanent members’, a subsequent practice has developed according to
which the abstention of a permanent member, which must be distinguished from a negative vote
(Veto), does not prevent the adoption of a resolution. In the ICJ advisory opinion Legal
Consequences for States of the Continued Presence of South Africa in Namibia (South West
Africa) notwithstanding Security Council Resolution 276 (1970) (Advisory Opinion) (‘Legal
Consequences of South Africa in Namibia’), the ICJ noted that this practice had been generally
accepted by the Member States of the UN.

E. Treaties, Termination

1. Limitations on the Right to Denounce or Terminate Treaties

71 Most, if not all, rules of the VCLT on termination codify customary international law. In the
interests of stability of treaty relations and the preservation of the principle pacta sunt servanda,
Art. 42(2) VCLT provides: ‘[t]he termination of a treaty, its denunciation or the withdrawal of a
party, may take place only as a result of the application of the provisions of the treaty or of the
present Convention’. Arts 54 and 56 VCLT provide for the possibility of termination according to the
VCLT and by consent of the parties, which are commonly adopted practices in modern treaty
practice. More controversial is Art. 56(1) VCLT, which covers the treaties without provisions on
termination, denunciation, or withdrawal. The main rule is that such a treaty cannot be denounced
or withdrawn from unless: ‘(a) it is established that the parties intended to admit the possibility of
denunciation or withdrawal; or (b) a right of denunciation or withdrawal may be implied by the
nature of the treaty’. It is uncertain whether this article reflects customary international law.

72 The VCLT distinguishes between denunciation of and withdrawal from a treaty without providing
a definition of the terms in Art. 2(1) or specifying the rationale of this distinction. Both relate to the
unilateral act of a State wishing to terminate a treaty in relation to itself. However, while
denunciation relates to both bilateral and multilateral treaties, withdrawal relates only to multilateral
treaties. The denunciation of a bilateral treaty puts an end to it, whereas denunciation of or
withdrawal from a multilateral treaty only means that the multilateral agreement is no more
applicable from the date of its withdrawal to the State in question.

2. Grounds for Termination

(a) Material Breach of Treaty

73 Art. 60 VCLT regulates the termination of a treaty for its alleged material breach. As a general
rule the breach of a treaty, however serious, does not ipso facto terminate the existence of a
treaty. But within certain limits, and subject to certain safeguards, the right of a party to invoke a
breach as a ground for terminating or suspending a treaty is recognized. Such rules were referred
to by the ICJ in Legal Consequences of South Africa in Namibia as being ‘in many respects’
considered to represent customary international law (at 47). The ICJ has generally supported a
restrictive view on the right to terminate a treaty on the grounds of material breach (see
Gabčikovo-Nagymaros Case).

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 74 The relationship between material breach and the law of State responsibility is problematic, in
particular in relation to the law concerning countermeasures. It appears that these two regimes
coexist independently. It is the general view that non-material breaches of a treaty may activate
the right to have recourse to countermeasures. However, as evidenced by the case-law, States do
not draw a clear line between the termination of a treaty on the grounds of material breach or as a
consequence of countermeasures (see The Air Services Agreement of March 27 1946 [United
States v France] arbitration and the Rainbow Warrior [New Zealand v France] arbitration; Rainbow
Warrior, The).

(b) Fundamental Change of Circumstances

75 Art. 62 VCLT regulates the impact of a fundamental change of circumstances on an
international agreement. The provision is drafted in a very narrow way in order to safeguard the
stability of treaties. Whether Art. 62 VCLT reflects customary international law is questioned. The
use of the clausula rebus sic stantibus clause, in particular invoking that the political system of the
State in question has changed, was perceived as posing a threat to the stability of international
treaty relations. In contemporary treaty relations, the rule of fundamental change of circumstances
is applied only in exceptional circumstances, which was confirmed by the ICJ in the 1997
Gabčikovo-Nagymaros Case. There is little jurisprudential guidance as to what constitutes a
fundamental change of circumstances. In academic writing it is agreed that a mere change of
governmental policy generally would not suffice to invoke the plea, nor would a change of political
regime, government, or administration. The plea of fundamental change of circumstances does not
terminate the treaty automatically but has to be invoked according to the procedures set out in Art.
65 VCLT.

(c) Supervening Impossibility of Performance

76 The supervening impossibility of performance is a well-established and uncontested ground for
the termination of a treaty, which was codified in Art. 61 VCLT. Art. 61 VCLT limits the ground to the
‘permanent disappearance or destruction of an object indispensable for the execution of the treaty’
and cannot be invoked by a party that was itself instrumental in causing the change of
circumstance by breach of an obligation under the treaty or of any other international obligation
owed to any other party to the treaty. It was upon the basis of this limitation that the ICJ in the
Gabčikovo-Nagymaros Case once again adopted a strict approach to the termination of treaty
obligations, denying Hungary’s right to invoke the impossibility of performance brought about by its
own failure to perform its obligations.

(d) Emergence of a New Peremptory Norm

77 A norm of ius cogens is, according to Art. 53 VCLT, a peremptory norm of general international
law which is accepted and recognized by the international community of States as a whole. Its
essential characteristic is that no derogation from it is permitted and that it can only be modified by
another subsequent norm of ius cogens. Accordingly, Art. 64 VCLT provides that a treaty which is
in conflict with a new norm of ius cogens becomes void and terminates. Art. 71 clarifies that such a
treaty does not become void retroactively. Examples of ius cogens are the prohibition of the use of
force in Art. 2(4) UN Charter, as well as the prohibition of the slave trade, genocide, piracy, and
torture; the principle of self-determination has also been suggested.

78 The theoretically opposite concept is that of ius dispositivum, ie law which is at the disposal of
States and can be modified by them at will: for instance, treaties concluded in order to deviate from
rules of customary international law, or reservations made to treaty provisions imply underlying ius
dispositivum. Also, the concept of ius cogens needs to be distinguished from that of obligations
erga omnes, especially so because some norms of international law are suggested to belong to
both categories. According to the ICJ in Barcelona Traction, Light and Power Co Ltd (Belgium v
Spain) (Second Phase) ([1970] ICJ Rep 3; Barcelona Traction Case), obligations erga omnes are,

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 ‘[b]y their very nature the concern of all States’ and therefore are owed to ‘the international
community as a whole’ (at 32). The erga omnes quality of a norm becomes relevant in the field of
State responsibility, and concerns the question of legal standing in case of their violation. Art. 48
UN ILC Draft Articles on Responsibility of States for Internationally Wrongful Acts ([2001] GAOR 56th
Session Supp 10, 43; ‘Draft Articles on State Responsibility’) deals with this matter, and certain
aspects of the article can be seen as involving a measure of progressive development of
international law. More precisely, Art. 48 Draft Articles on State Responsibility provides that in case
of breach of an obligation erga omnes any State is entitled to invoke the responsibility of the
apparently breaching State, and to claim from the responsible State not only the cessation of the
internationally wrongful act, but also the performance of any obligation of reparation, in the interest
of the injured State or the beneficiaries of the obligation breached.

(e) The Effects of Armed Conflict on Treaties

79 The VCLT does not deal with the effects of armed conflict on treaties (Armed Conflict, Effect on
Treaties). Traditionally, the view was expressed that the legal status of bilateral and multilateral
treaties during the armed conflict should be distinguished. As a principle, peace treaties provide for
the solution in relation to the pre-war treaties. The ILC at its 52nd session took up the topic ‘Effects
of Armed Conflicts on Treaties’ for future work and appointed Professor I Brownlie as Special
Rapporteur. In 2005, Brownlie presented a set of Draft Articles (UN ILC Special Rapporteur I Brownlie
‘First Report on the Effects of Armed Conflicts on Treaties’ [21 April 2005] UN Doc A/CN.4/552). The
ILC supported the views of the Special Rapporteur encouraging the continuity of treaty obligations
in the event of armed conflict, provided there was no necessity for suspension or termination. The
ILC took the view that the somewhat outdated doctrine from the past, which tended to impair such
continuity, should not be rigidly relied on. The ILC also endorsed the view that it is better to review
the problem of the effect of the armed conflict on treaties from the point of view of particular
provisions and circumstances than to rely on any general rules, holding it more useful to identify
the considerations which a State should take into account in the circumstances, rather than
attempting to establish definite inflexible rules that States must always follow. The Special
Rapporteur held the view that there was no good reason for establishing special criteria for bilateral
and multilateral treaties. According to his view, the intention of the parties should be decisive (First
Report on the Effects of Armed Conflicts on Treaties at para. 5).

(f) Extinction of a Party

80 The extinction of a party as a ground for the termination of a treaty is not mentioned in the
VCLT. It will be of importance in practice only in relation to bilateral treaties.

(g) Desuetude
81 Desuetude as a way of terminating a treaty is not regulated by the VCLT (Desuetudo). This
means that the termination of a treaty may be implied if it is clear from the conduct of the parties
that they no longer consider the treaty as binding.

3. Other General Issues Relating to the Termination of Treaties

(a) Loss of Right to Invoke a Ground for Invalidating, Terminating,

Withdrawing from, or Suspending the Operation of a Treaty
82 Art. 45 VCLT sets out the conditions under which the right to invoke a ground for invalidating,
terminating, withdrawing from, or suspending the operation of a treaty can no longer be exercised.
There are very few cases relating to the application of the principle underlying Art. 45 VCLT,
however, those cases do not strictly relate to treaties but to, for example, the validity of arbitral
awards (Arbitral Award Made by the King of Spain on 23 December 1906 [Honduras v Nicaragua]
[1960] ICJ Rep 192), of maps attached to treaties (Temple of Preah Vihear Case), or commercial

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 contracts between States and non-State entities (Textron Inc and Bell Operations Corporation v
Islamic Republic of Iran [Arbitral Award] [12 February 1981] [1984] 6 Iran-US CTR 328, vol II).

(b) Consequences of the Termination of a Treaty

83 Art. 70 VCLT regulates the consequences of the termination of a treaty. This article should be
read together with the general provisions of Sec. 1, Part V VCLT (especially Arts 42(2)–44 VCLT).
There is no case-law directly addressing Art. 70 VCLT. However, in the 1990 award in the Rainbow
Warrior (New Zealand v France), Art. 70 VCLT was referred to as customary international law.

(c) Procedure to be Followed with Respect to Invalidity, Termination,

Withdrawal from, or Suspension of the Operation of a Treaty
84 Arts 65–8 VCLT (Sec. 4, Part V VCLT) set out the procedure to be followed with respect to
invalidity, termination, withdrawal from, or suspension of the operation of a treaty (Treaties,
Suspension). The ICJ in the 1997 Gabčíkovo-Nagymaros Case considered these provisions as not
constituting customary international law. Art. 65 VCLT is a chapeau to the rest of Sec. 4 and lays
down the general procedure to be followed in this respect. In case no agreement is reached under
Art. 65 VCLT, Art. 66 VCLT sets out specific procedures for judicial settlement, arbitration (only for
disputes relating to ius cogens), and conciliation (all remaining disputes). Art. 67 VCLT sets out
instruments for declaring invalid, terminating, withdrawing from, or suspending the operation of a
treaty. Finally, according to Art. 68 VCLT, a notification or instrument mentioned in Arts 65 or 67
VCLT may be revoked at any time before it takes effect.

F. Treaties, Interpretation

1. General Principles
85 Treaty interpretation is to some extent regulated by the VCLT, nevertheless, many problems
remain controversial.

86 A fundamental set of principles of interpretation of treaties was proposed by Sir G Fitzmaurice,

who based it on the practice of the ICJ. These are as follows: Principle I: of actuality—that treaties
have to be interpreted as they stand, on the basis of their actual text. Principle II: the natural and
ordinary meaning—that subject to the principle of contemporaneity (where applicable), particular
words and phrases are to be given their normal, natural, and unrestrained meaning in the context
in which they occur. This principle can only be displaced by direct evidence that the terms used
are to be understood in a manner different to their natural and ordinary meaning, or if such an
interpretation would lead to an unreasonable or absurd result. Principle III: integration—that treaties
are to be interpreted as a whole. This principle is of fundamental importance and means that
individual parts, chapters, or sections of a treaty are not to be interpreted out of their overall
context. The remaining principles take effect subject to the three principles outlined above. These
are: Principle IV: effectiveness (ut magis valeat quam pereat)—that treaties are to be interpreted
with reference to their declared or apparent objects and purposes; and particular provisions are to
be interpreted so as to give them the fullest effect consistent with the normal sense of the words
and with the text in such a way that a reason and meaning can be attributed to every part of the
text. Principle V: subsequent practice—that recourse may be had to subsequent practice of parties
relating to the treaty. Principle VI: contemporaneity—that the terms of a treaty must be interpreted
in the light of linguistic usage current at the time when the treaty was concluded.

2. Three Schools
87 In general there may be said to exist three general schools of, or approaches to, interpretation:
the subjective (the ‘intention’ of the parties) approach; the objective (the ‘textual’) approach; and

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 the teleological (the ‘object and purpose’) approach. These three schools of interpretation are not
mutually exclusive and the VCLT draws on all three. However, it is debatable whether the VCLT
successfully combined the objective and subjective approaches, which in the view of many appear
to be effectively irreconcilable. The ILC adopted the ‘textual’, rather than the ‘intention of the
parties’ approach, on the basis that it is to be presumed that the text represents the real
expression of what the parties in fact intended.

88 The ICJ has consistently adhered to the textual interpretation as being the most important, as in
the Territorial Dispute Case (Libyan Arab Jamahiriya/Chad), where it stated as follows:
‘Interpretation must be based above all upon the text of the treaty. As a supplementary measure
recourse may be had to means of interpretation such as the preparatory work’ (at 22). The
determination of the ordinary meaning of the term is undertaken in the context of the treaty as a
whole and in the light of its object and purpose (see eg Interpretation of the Convention of 1919
Concerning Employment of Women during the Night [Advisory Opinion] PCIJ Series A/B No 50).

89 In many cases, the ICJ has stated that, ‘in accordance with customary international law,
reflected in Article 31 of the VCLT, a treaty must be interpreted in good faith in accordance with the
ordinary meaning to be given to its terms in their context and in the light of its object and purpose’
(see eg the 1994 [Territorial Dispute Case [Libyan Arab Jamahiriya/Chad] at 19–20; Good Faith
[Bona fide]). The underlying principle is that the treaty is to be interpreted in good faith, which is the
embodiment of the principle pacta sunt servanda.

3. Object and Purpose

90 According to the general rule on interpretation in Art. 31(1), a treaty shall also be interpreted in
the light of its object and purpose. As already mentioned in the context of reservations,
considerable uncertainty surrounds the determination of a treaty’s object and purpose. Despite
frequent references to the criterion, the jurisprudence of several international courts and tribunals
(including the Permanent Court of International Justice [PCIJ], the ICJ, and others) has not clarified
the existing ambiguities. In academic writing, it is contested whether the terms ‘object and purpose’
are synonymous (English and German writers) or not (French writers). According to the latter view,
‘object’ refers to the content of the treaty, while ‘purpose’ designates the overall aim to be
achieved by means of the treaty. Furthermore, the methodology for establishing a treaty’s object
and purpose is far from clear. In the jurisprudence, recourse has been had, inter alia, to the
following criteria, individually or cumulatively: the title of the treaty; its preamble; an article of the
treaty with apparent relevance for the treaty’s object and purpose; and the travaux préparatoires;
etc.

4. Place of Subsequent Practice

91 Another problem concerns what is to count as constituting subsequent practice for the
purposes of interpretation, the use of which is sanctioned as forming part of the context of the
treaty by Art. 31(3) VCLT. In the 1999 Kasikili/Sedudu Island Case (Botswana/Namibia), the ICJ
adhered to the view that the subsequent practice of parties to a treaty constitutes an element to be
taken into account when determining its meaning, but it adopted a restrictive approach to what
comprises subsequent practice and did not take into account unilateral acts of the previous
authorities of Botswana on the grounds that these were for internal purposes only and unknown to
the Namibian authorities.

5. Place of Traveaux Préparatoires

92 One of the most controversial issues in treaty interpretation is the use of travaux préparatoires
(preparatory work). The VCLT gives very specific conditions under which travaux préparatoires
may be used: either to confirm the meaning of the treaty or as an aid to interpretation where,

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 following the application of Art. 31 VCLT, the meaning is obscure or leads to a result which is
manifestly absurd or unreasonable. The ICJ has always made very restrictive use of travaux
préparatoires. This approach, however, has given rise to the view that the ICJ has not always
established sufficiently the requisite common intention of the parties (see the 1995 Maritime
Delimitation and Territorial Questions between Qatar and Bahrain [Qatar v Bahrain] [Dissenting
Opinion of Vice-President Schwebel]; Case between Qatar and Bahrain [1995]).

6. Principle of Effectiveness
93 The principle of effectiveness in treaty interpretation is closely related to the notion of the
‘object and purpose’ of the treaty. This is, however, a very ill-defined term, making it an unreliable
tool for interpretation. The principle of effectiveness is enshrined in the maxim: magis valeat quam
pereat. Although this principle can operate as an element within the object and purpose principle, it
is not limited to this role. The ICJ has used it to ascertain the intention underlying a treaty and as a
broader point for discussion.

7. Principle of Systematic Integration

94 This principle derives from Art. 31(3)(c) VCLT and requires the interpretation of the treaty in the
light of ‘any relevant rules of international law applicable in the relations between the parties’. This
principle was one of the most neglected issues of treaty interpretation. However, it gained
importance in relation to the fragmentation of international law, its diversification, and expansion.

95 The question of treaty interpretation is currently under consideration by the ILC and came up
during its work on the topic ‘Fragmentation of International Law: Difficulties Arising from the
Diversification and Expansion of International Law’ (UN ILC ‘Fragmentation of International Law:
Difficulties Arising from the Diversification and Expansion of International Law: Report of the Study
Group’ [17 July 2006] GAOR 61st Session Supp 10, 403).

8. Inter-temporal Law
96 Art. 31 (3) (c) VCLT is also concerned with inter-temporality (Intertemporal Law), a theory which
originated in M Huber’s reasoning in the Palmas Island Arbitration (Island of Palmas Case
[Netherlands v United States of America]), and which may be defined in the words of Judge Huber
where he says: ‘a juridical fact must be appreciated in the light of the law contemporary with it, and
not of the law in force at the time when a dispute in regard to it arises or falls to be settled’; and he
says further:

As regards the question which of different legal systems prevailing at successive periods is
to be applied in a particular case (the so-called intertemporal law), a distinction must be
made between the creation of rights and the existence of rights. The same principle which
subjects the act creative of a right to the law in force at the time the right arises, demands
that the existence of the right, in other words its continued manifestation, shall follow the
conditions required by the evolution of law (at 845).

G. Effect of Treaties on Third Parties

1. The General Rule

97 The fundamental principle relating to the effect of treaties on third States is contained in the
maxim pacta tertiis nec nocent nec prosunt, which means that treaties have no legal effect on third
States (Treaties, Third-Party Effect). Treaties are res inter alios acta for these States. This main rule
is embodied in Art. 34 VCLT: ‘[a] treaty does not create either obligations or rights for a third State

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 without its consent’.

2. Treaties Providing for Rights and Obligations for Third States, and
Treaty Rules Becoming Binding on Third States through International
Custom
98 Art. 35 VCLT codifies the rule on treaties providing for obligations for third States. An obligation
may arise from a treaty for third States if two conditions are fulfilled: the parties to the treaty
intended the provision to be the means of establishing the obligation and the third State expressly
accepts the obligation in writing. However, the possibility of concluding a treaty imposing
obligations on third States, even on the basis of the above-mentioned conditions, is not without
controversy.

99 Rights derive from a provision of a treaty for a third State, if the parties so intended and the
third State assents thereto (Art. 36 VCLT). Assent may be presumed ‘so long as the contrary is not
indicated, unless the treaty otherwise provides’ (Art. 36 VCLT). Possibly, one of the examples of
such a situation would be the most-favoured-nation clause.

100 Finally, a rule set out in a treaty may be (or become) binding on third States as a rule of
customary international law (Art. 38 VCLT). In the 1969 North Sea Continental Shelf Cases, the ICJ
described different ways in which treaties and customary international law may interact, and
recognized the possibility of the existence of identical rules in international treaty law and
customary international law. (On this last point, see also the Nicaragua Case 95–6).

3. Objective Regimes
101 One of the unresolved and controversial issues, which is not included in the VCLT, remains
the problem of treaties establishing so-called objective regime[s], ie regimes which are opposable
to all States. Examples of such treaties are those establishing the demilitarized zones
(Demilitarization). There is also the view that the legal regime on Antarctica is an objective regime
(see eg E Klein Statusverträge im Völkerrecht: Rechtsfragen Territorialer Sonderregime [Springer
Berlin 1980]).

H. Miscellaneous Matters

1. Treaties, Territorial Application

102 Territorial application of treaties is governed by Art. 29 VCLT: ‘[u]nless a different intention
appears from the treaty or is otherwise established, a treaty is binding upon each party in respect
of its entire territory’ (Treaties, Territorial Application). This rule appears to codify existing
international law. The question may arise of whether the expression ‘its entire territory’ only refers
to areas fully under a State’s sovereignty or also to territories with respect to which that State has a
certain international responsibility including treaty-making power (eg protectorates and protected
States). Mention must be made of the so-called ‘colonial clause’, which is largely of historical
relevance, by virtue of which the territorial application of treaties is regulated in respect to
territories for which parties are responsible. Territorial application of treaties may change with a
change in the status of the territory.

2. Treaties, Registration, Publication, and Depositary

(a) Registration
103 The obligation of States with regard to registration of treaties is regulated by Art. 102 UN

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 Charter (Treaties, Registration and Publication). It is the responsibility of the States Parties to a
treaty to register it. Despite the prohibition contained in Art. 102 UN Charter of relying on any
unregistered treaties before any organ of the UN, the ICJ has not adopted a strict and uniform policy
towards non-registered treaties. Art. 80 VCLT does not provide any sanctions for non-registration.

104 It is sometimes suggested that the registration of an instrument in accordance with Art. 102
UN Charter is an indication of it being an international treaty. However, it is not a reliable indicator,
as on one hand the UN Secretariat registers almost all documents submitted to it, including
unilateral declarations, and on the other hand not all treaties are registered. This is also a view
expressed by the ICJ in the Case between Qatar and Bahrain: 1994, in which the fact of non-
registration was held not to be decisive as to the character of the document in question (at 122).

(b) Publication
105 While the obligation to register treaties under Art. 102(1) UN Charter is primarily on the UN
Member States, the publication of such registered treaties is the responsibility of the UN Secretariat.
It is questionable whether Art. 102 UN Charter had a direct effect on the reduction of the number of
secret treaties (Treaties, Secret). To the extent there has been such a reduction, it is rather a result
of the changed political climate, and greater transparency in relations between States and modern
diplomacy.

(c) Depositaries
106 A depositary is the custodian of the original text of the treaty and mainly acts as an
administrator of the treaty. States or international organizations can act as the depositary of
treaties. The UN Secretary-General often acts in this capacity in relation to multilateral treaties. Art.
71(1) VCLT lists the principal functions of a depositary. Among these is the receipt of notifications
and communications of the parties to the treaty (Art. 78 VCLT), which may include notifications on
the ratification, on reservations, or the withdrawal of a party from the treaty. The depositary may
also notify the parties of errors and of proposals to correct them.

(d) Treaty Series

107 Prior to the commencement of the UN Treaty Series, the most important publication of treaties
and treaty material was the ‘Martens Recueil de Traites’ which was published from 1791 until 1934
(from 1881, renamed ‘Martens Nouveau Recueil des Traites’). The League of Nations Treaty Series
was published from 1919 until it was superseded by the UN Series in 1947.

3. Treaties, Conflicts Between

(a) General Rules

108 A conflict between treaties arises when those treaties include incompatible provisions for
parties to both of them (Treaties, Conflicts between). For this situation to arise, it is possible but not
necessary that those treaties relate to the same subject-matter. The question of incompatibility of,
or conflict between, treaties is first a matter of interpretation. Relevant in this context is Art. 31(3)(c)
VCLT according to which, for the interpretation of a treaty, the relevant rules of international law
applicable between the parties shall be taken into account.

109 Conflicts between treaties is one of the most difficult areas of the law of treaties, which
historically received little attention and still involves many unresolved issues. However, certain
rules have evolved. There are several maxims relating to conflict of treaties: lex posterior derogat
legi proiri; lex specialis derogat legi generali; prior in tempore, potior in jure. These were widely
used in the jurisprudence of the ICJ.

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 110 The VCLT deals with the conflict of treaties in several provisions. The rules relating to the
application of successive treaties contained in Art. 30 VCLT relate only to the conflict of successive
treaties relating to the same subject-matter. In itself, Art. 30 VCLT leaves many issues unresolved.
The following questions remain. How strictly is the ‘same subject-matter’ requirement to be
interpreted? What is the practical application of Art. 30 VCLT in relation to Art. 41 VCLT
(agreements to modify multilateral treaties between certain parties only) and Art. 59 VCLT
(termination or suspension of the operation of a treaty implied by conclusion of a later treaty)? Arts
53 and 64 VCLT regulate the special case of the conflict of a treaty with a norm of ius cogens,
which links the problem to the invalidity of treaties. However, the VCLT does not address the
question of conflict between treaties relating to different subject-matters.

111 Art. 103 UN Charter sets out a hierarchical principle according to which in case of conflict
between obligations of parties under the UN Charter and their obligations under any other
international agreements, the former prevails. The drafting of Art. 103 leads to several
uncertainties, such as the legal effects of treaty provisions incompatible with the UN Charter
(whether suspended, unenforceable, voidable, or void) or whether the UN Charter prevails over
incompatible obligations derived from customary international law or undertaken by way of
unilateral act. It is also unclear to which UN Charter obligations Art. 103 refers, whether only to
those within the UN Charter itself, or also to those resulting from binding decisions of UN organs
(such as UN Security Council Chapter VII resolutions).

112 It is also unclear whether Art. 103 UN Charter is intended to affect obligations from treaty
relations which involve non-Member as well as Member States.

113 There is little ICJ jurisprudence on Art. 103 UN Charter, and the ICJ’s first reference to Art. 103
was made only in passing in the Nicaragua Case. However, when indicating provisional measures
in the Lockerbie Cases (Libyan Arab Jamahiriya v United Kingdom and United States of America),
the ICJ clarified one of the above-mentioned uncertainties, namely that those obligations ‘under the
UN Charter’ which prevail according to Art. 103 UN Charter indeed encompass obligations arising
from binding decisions adopted by UN organs, as in this instance a UN Security Council Chapter VII
resolution (Questions of Interpretation and Application of the 1971 Montreal Convention Arising
from the Aerial Incident at Lockerbie [Libyan Arab Jamahiriya v United Kingdom] [Preliminary
Objections] [1998] ICJ Rep 9; Questions of Interpretation and Application of the 1971 Montreal
Convention Arising from the Aerial Incident at Lockerbie [Libyan Arab Jamahiriya v United States
of America] [Preliminary Objections] [1998] ICJ Rep 115).

(b) Conflict Clauses or Savings Clauses

114 It is now relatively common in multilateral treaties to insert so-called ‘conflict clauses’ which
are intended to make express provisions to resolve problems arising from a conflict between
treaties (Treaties, Conflict Clauses). They are also referred to as ‘savings’ or ‘compatibility’
clauses. Examples of such clauses can be found in the preamble of the Cartagena Protocol on
Biosafety to the Convention on Biological Diversity ([done 29 January 2000, entered into force 11
September 2003] (2000) 39 ILM 1027), which states that ‘this Protocol shall not be interpreted as
implying a change in the rights and obligations of a Party under any existing international
agreements’; Art. 311(1) UN Convention on the Law of the Sea; Art. 73 Vienna Convention on
Diplomatic Relations ([done 18 April 1961, entered into force 24 April 1961] 500 UNTS 95); Art. 137
Charter of the Organization of American States ([signed 30 April 1948, entered into force 13
December 1951] 119 UNTS 3); and Art. 8 North Atlantic Treaty ([signed 4 April 1949, entered into
force 24 August 1949] 34 UNTS 243) among others. The possibilities relating to these conflict
clauses are quite complex, and in certain of the possible situations, their effect is not entirely clear.
In the first place, the conflict clause may be included in either an earlier or a later treaty, or indeed
in both. And whichever treaty the clause is included in, it may be aimed either a) at ensuring the
priority of the later treaty (in which case it may in fact do no more than give expression to the

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 general lex posterior rule; b) at preserving the effect of the earlier treaty; or c) if actually included
in the earlier treaty, at preventing States Parties from entering into agreements in the future which
conflict with the earlier treaty. It has to be said that not all potential conflicts can be solved by the
application of the relevant principles, in the case of mutually exclusive obligations.

4. Treaties, Unequal
115 The concept of ‘unequal treaties’ is really a historical phenomenon, having arisen in practice
in the colonial context, although in principle it might arise in a wider context (Treaties, Unequal). In
general it may be said that a common feature of such treaties is a deviation from the principle of
the sovereign equality of States (States, Sovereign Equality). It may also mean that the principle of
reciprocity is not observed. The VCLT does not cover this topic expressly, however, the principle
of the ‘unequal treaty’ may be invoked as a ground of invalidity, on the basis of Art. 52 VCLT
(coercion of a State by threat or use of force), Art. 53 VCLT (conflict with a peremptory norm of
international law, ius cogens), or as a ground for termination, on the basis of Art. 62 VCLT
(fundamental change of circumstances).

5. Treaties, Succession

(a) Background
116 The succession of States to treaties is one of the uncertain areas in contemporary
international law (State Succession in Treaties). First, it is a complex subject, due to the widely
varying circumstances in which a succession of States may occur, the numerous different forms of
treaties which may be involved, and the varying stages, in terms of coming into force (eg not in
force or awaiting ratification) which they may have reached. Secondly, as was recognized by the
ILC throughout its work on the subject, there was little, if any, relevant State practice in the field, let
alone existing rules of customary international law. Thus the VCSS-T involves a significant amount
of progressive development. While the VCSS-T had widespread support in the ILC and UN General
Assembly (and is in force), it has received comparatively few ratifications. Thus instances of
succession of States will continue to occur to which rules of customary international law will apply.
Indeed, this was largely the case in relation to succession of States arising out of the break up of
the Union of Soviet Socialist Republics (‘Soviet Union’) and the former Socialist Federal Republic of
Yugoslavia (‘Yugoslavia’; Yugoslavia, Dissolution of). In this respect, the progressive development
solutions of the VCSS-T do accord to some extent with modern views on international law, in
particular the weight now given to the sanctity of treaties by comparison to the sovereign
independence of States. But while trends in State practice can be discerned, it is still too early to
say that rules of customary international law have yet emerged.

117 In relation to succession to treaties, one may distinguish several categories of treaties which
are governed by different rules of succession. For instance in relation to territorial treaties, different
rules will govern succession in the case of transfer of territory and different rules apply in relation
to so-called objective territorial regimes and boundary regimes, which are excluded from the
normal rules of State succession (Arts 11, 12 VCSS-T). Some provisions of the VCSS-T also make a
distinction between multilateral and bilateral treaties, and there are also some special rules relating
to treaties constituting international organizations and treaties adopted within international
organizations.

(b) The 1978 Vienna Convention on Succession of States in Respect to

Treaties (‘VCSS-T’)

(i) Transfers of Territory (Part II, Art. 15 VCSS-T)

118 Territorial changes may affect treaty regime (Territorial Change, Effects of). The rules of State

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 succession apply if territorial change results in a change of identity of a State or accords treaty
rights and obligations to other new or old subjects of international law.

119 The fundamental principle in the area of treaties and territorial changes is the so-called
‘moving treaty frontiers rule’, which means that a treaty moves together with the territory to the
successor State, thus leaving the territory of the predecessor State. This may be said to be a rule
of customary international law and is adopted as well in Art. 15 VCSS-T. This principle served as the
general rule for all international treaties of Germany and was set out in Art. 11 Treaty on the Final
Settlement with Respect to Germany ([signed 12 September 1990, entered into force 15 March
1991] 1696 UNTS 115; Germany, Unification of). Art. 11 Treaty on the Final Settlement with Respect
to Germany roughly provided that those international treaties not only retained their validity but that
their application was extended to the territories of the former German Democratic Republic. In
general, although widely accepted, the application of this rule is not without difficulties and some
problems may arise, such as the implementation of certain localized treaties.

120 The automatic operation of this rule is excluded with respect to dependent territories such as
colonies, protectorates, mandates, or trust territories (United Nations Trusteeship System) and in
the event of the dismemberment of a State, such as in the cases of the former Yugoslavia and the
Soviet Union.

(ii) The Uniting of States, the Dissolution of a State, and the Separation of Part of a State
(Part IV, Arts 31–38 VCSS-T)
121 With respect to the uniting of States, the dissolution of a State, and the separation of a part of
a State, the VCSS-T applies broadly a principle of automatic continuity of treaties—ie treaties which
were in force with respect to the territory to which the succession applies remain in force with
respect to that territory, with the successor State becoming a party to the treaty. This provision did
not reflect any rule of customary international law, nor even State practice. It did, however, reflect
a growing emphasis being placed on the sanctity of treaties.

122 It has to be noted that these positive provisions were subject to a number of important
exceptions (eg generally they do not apply if their operation would be incompatible with the object
and purpose of the treaty in question or would radically change the conditions for its operation).
There are also special provisions, in each case, relating to bilateral treaties and to treaties not yet
fully in force. The VCSS-T also generally does not apply to certain types of situations (eg arising as
a result of the outbreak of hostilities or military occupation [Art. 39 VCSS-T]); nor do the provisions
of the VCSS-T apply, in general, in a way which would affect any boundary or other territorial
regime (Arts 11, 12 VCSS-T).

(iii) Newly Independent States (Part III, Arts 16–30 VCSS-T)

123 At the outset of the ILC’s work on the subject, emphasis was laid on the issue of treaty
succession in relation to the independence of former colonial (or otherwise dependent) territories;
and the VCSS-T as concluded contains special provisions in this respect, notwithstanding that it
was recognized that the period of decolonization was virtually over and that the provisions would
apply to few instances in the future. The basic position adopted here was the so-called tabula rasa
(‘clean slate’) principle, according to which treaties that had been in force with respect to a
predecessor State would not automatically become applicable to the successor State, which would
come into existence free of all treaty rights and obligations applicable to the predecessor State
(Art. 16 VCSS-T). The VCSS-T further provided that the newly independent State would,
nevertheless have a right, by notification of succession, to establish its status as a party to any
multilateral treaty in force in relation to the territory concerned.

124 These provisions are considered as reflecting at least a widespread State practice, if not
actually an established rule of customary international law.

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 (c) The Current Status of the International Law in Relation to Treaty
Succession
125 As referred to above, the small number of ratifications of the VCSS-T means that rules of
customary international law, independently of the VCSS-T, will still be applicable in cases of treaty
succession which may arise. In fact, the question of the succession of bilateral treaties in the case
of the disappearance of one of the State Parties was raised in the Gabčíkovo-Nagymaros Case, in
which the status of Art. 34 VCSS-T (a rule of continuity of treaties) and Art. 12 VCSS-T (other
territorial regimes) in relation to contemporary customary international law was discussed. The ICJ
did not make a pronouncement on the legal status of Art. 34 VCSS-T; but considered that Art. 12
VCSS-T does reflect international customary international law. A similar situation arose in the
Application of the Convention on the Prevention and Punishment of the Crime of Genocide
(Bosnia and Herzegovina v Yugoslavia) (Preliminary Objections) [1996] ICJ Rep 595; Application
of the Convention on the Prevention and Punishment of the Crime of Genocide Case [Bosnia and
Herzegovina v Serbia and Montenegro]) in 1993, in relation to a multilateral convention. Again, the
ICJ did not pronounce on the legal status of Art. 34 VCSS-T, though in this case support was given
for the concept of continuity of treaties in a number of dissenting or separate opinions.

I. Assessment
126 The law of treaties constitutes one of the three pillars of international law together with
sources of international law and the law of State responsibility. Treaties are the most commonly
used means of creating binding norms between sovereign States. Some of the areas of
international law are almost exclusively regulated by treaties, such as international environmental
law, in which customary international law plays a minor role. The relationship between treaties and
customary international law is of fundamental importance, in particular in cases of multilateral
treaties, which are intended to give rise to a norm of customary international law, a process which
has to be treated with great caution.

127 The basic principle of the law of treaties, pacta sunt servanda, remains the fundament on
which the whole of the system of treaty obligations is built. The most authoritative source of the
rules concerning the law of treaties is the VCLT, in most parts representing existing customary
international law. However, some issues remain unresolved, such as the question of reservations,
in particular reservations to human rights treaties, a problem which is at present on the agenda of
the ILC. Some questions are not within the remit of the VCLT, such as unequal treaties or the effect
of armed conflict on the law of treaties, which remains one of the unresolved issues and therefore
currently also under the consideration of the ILC. There are other problems which present
difficulties, such as the relationship between the material breach of a treaty and the international
law of countermeasures, as well as the role of travaux préparatoires in the interpretation of
treaties. The question of the succession to treaties is not fully resolved either, and it is common
ground between States that the VCSS-T only in part codifies existing customary international law.

128 Many points of the law of treaties are still being clarified and crystallized by international
courts and arbitral tribunals, in particular the ICJ, as well as by the monitoring bodies established on
the basis of multilateral human rights agreements, in areas such as the reservation to treaties, the
rule of treaty interpretation, the termination and invalidity of treaties, and the relationship between
the rules of the law of treaties and those of State responsibility. Some treaties are living instruments
and therefore their application by courts and tribunals, as well as States’ practice, contributes to
their further development and a better understanding of how they work. Further, the contribution of
international organizations to the development of treaties must be noted, as well as that of the
European Union, specifically the unique way in which it created a particular system of treaties
(European Community, Mixed Agreements). The EU applies the law of treaties and the VCLT, and
therefore participates in its interpretation and elaboration.

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 129 It also must be observed that the work of the ILC in other areas than the law of treaties also
contributes to its development and crystallization, for instance in relation to the topic of
‘Fragmentation of International Law: Difficulties Arising from the Diversification and Expansion of
International Law’, in which the ILC analyses Arts 31(3)(c), 30 (application of successive treaties
relating to the same subject-matter), and 41 VCLT.

130 International treaties now fulfil a very wide range of purposes, in particular providing at the
international level many of the functions fulfilled by acts of parliament or other legislation at the
municipal level. Treaties and binding decisions of international organizations are the vehicle
whereby States can deliberately make rules or dispositions among themselves which are binding in
international law. Contemporary international relations are characterized by the expansion of
treaties, in particular in areas such as international environmental law, international economic law,
international law of the sea, and international criminal law.

131 Moreover, there are several features of the treaty-making process which may put in doubt the
appropriateness of treaties as the main tool for regulating international relations. The conclusion
and entry into force of international treaties may be a lengthy procedure making it difficult to
respond quickly to new challenges. Striving for the universality of a treaty may result in allowing
reservations which in turn further weaken the effectiveness of the treaty. Considering the increase
of international treaties and their growing impact on national law, their legitimacy has been called
into doubt. One may wonder whether the cure—if a cure is needed at all—may rest in national
rather than international law. The law of treaties itself addresses the problem of the possibly lengthy
treaty-making procedure by providing for the provisional application of treaties under Art. 25 VCLT.

132 Since treaties only bind the participating parties, it is difficult to effectively regulate issues
considered to be of global concern, such as climate change.

133 States have tried to overcome the inherent deficiencies of the treaty-making procedure or
treaties themselves by devising ways to make treaties reflect more accurately the political,
economic, and social realities, and to respond to scientific progress or other changes in general.
Examples of such devices may be found, for example, in international environmental law, where
States developed new mechanisms of expressing consent to be bound, thereby making those
treaties more flexible. This, however, in turn may lead to questions regarding the legitimacy of
norm-making power by organs created by multilateral environmental treaties. Framework
agreements reflect the phenomenon that sometimes only an agreement on general principles was
reached. Such framework agreements may later be supplemented by additional protocols or
implementation agreements negotiated sometimes in conferences reflecting a particular expertise.

Select Bibliography
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P Chailley La nature juridique des traités internationaux selon le droit contemporain
(Recueil Sirey Paris 1932).
AF Frangulis Théorie et pratique des traités internationaux (Réd Administration Paris 1934).
AD McNair The Law of Treaties (Clarendon Oxford 1961).
I Detter Essays on the Law of Treaties (PA Norstedt & Söners Förlag Stockholm 1967).
RD Kearney and RE Dalton ‘The Treaty on Treaties’ (1970) 64 AJIL 495–561.
S Rosenne The Law of Treaties: A Guide to the Legislative History of the Vienna
Convention (Sijthoff Leyden 1970).
A Maresca Il diritto dei trattati: la convenzione codificatrice di Vienna del 23 maggio 1969
(Giuffrè Milano 1971).
H Blix and JH Emerson (eds) The Treaty Maker’s Handbook (Oceana Dobbs Ferry 1973).

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2015. All Rights Reserved. Subscriber:
Oxford University Press - Master Gratis Access; date: 09 January 2016
 G Haraszti Some Fundamental Problems of the Law of Treaties (Akadémiai Kiadó Budapest
1973).
TO Elias The Modern Law of Treaties (Oceana Dobbs Ferry 1974).
RG Wetzel and D Rauschning The Vienna Convention on the Law of Treaties: Travaux
Préparatoires (Metzner Frankfurt am Main 1978).
EW Vierdag ‘The Law Governing Treaty Relations between Parties to the Vienna Convention
on the Law of Treaties and States not Party to the Convention’ (1982) 76 AJIL 779–801.
W Karl Vertrag und spätere Praxis im Völkerrecht (Springer Berlin 1983).
JF Rezek Direito dos Tratados (Forense Rio de Janeiro 1984).
I Sinclair Vienna Convention on the Law of Treaties (2nd ed Manchester University Press
Manchester 1984).
S Bastid Les traités dans la vie internationale: Conclusions et effets (Economica Paris
1985).
H Isak and G Loibl ‘United Nations Conference on the Law of Treaties between States and
International Organizations or between International Organizations’ (1987) 38
Österreichische Zeitschrift für Öffentliches Recht und Völkerrecht 49–78.
FG Jacobs and S Roberts (eds) The Effect of Treaties in Domestic Law (Sweet & Maxwell
London 1987).
A Remiro Brotons Derecho internacional público vol 2 Derecho de los Tratados (Tecnos
Madrid 1987).
S Rosenne Developments in the Law of Treaties 1945–1986 (CUP Cambridge 1989).
J Combacau Le droit des traités (PUF Paris 1991).
PK Menon The Law of Treaties between States and International Organizations (Mellen
Lewiston 1992).
MG Monroy Cabra Derecho de los Tratados (2nd ed Ed Leyer Bogota 1995).
P Reuter Introduction au droit des traités (3rd ed Presses Universitaires de France Paris
1995).
J Klabbers The Concept of Treaty in International Law (Kluwer The Hague 1996).
E de LaGuardia Derecho de los tratados internacionales (Abaco Buenos Aires 1997).
O Elias and C Lim ‘The Role of Treaties in the Contemporary International Legal Order’ (1997)
66 NordicJIL 1–21.
ME Villiger Customary International Law and Treaties: A Manual on the Theory and Practice
of the Interrelation of Sources (2nd ed Kluwer The Hague 1997).
J Klabbers and R Lefeber (eds) Essays on the Law of Treaties: A Collection of Essays in
Honour of Bert Vierdag (Nijhoff The Hague 1998).
V Gowlland-Debbas (ed) Multilateral Treaty-Making: The Current Status of Challenges to
and Reforms Needed in the International Legislative Process (Nijhoff The Hague 2000).
A Watts (ed) The International Law Commission 1949–1998 vols 2–3 (OUP Oxford 2000).
P Dallari Constituição e tratados internacionais (Editora Saraiva São Paulo 2003).
S Davidson (ed) The Law of Treaties (Ashgate Aldershot 2004).
V Mazzuoli Tratados internacionais (com comentários à Convenção de Viena de 1969) (2nd
ed Oliveira São Paulo 2004).
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Law of Treaties (Wolf Legal Publishers Nijmegen 2005).
N Matz Wege zur Koordinierung völkerrechtlicher Verträge—Völkervertragsrechtliche und
institutionelle Ansätze (Springer Berlin 2005).
R Wolfrum and V Röben (eds) Developments of International Law in Treaty Making
(Springer Berlin 2005).
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2005).
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Law (2nd ed OUP Oxford 2006) 187–213.
A Pellet ‘Article 38’, in A Zimmerman, C Tomuschat, and K Oellers-Frahm (eds), The Statute of

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2015. All Rights Reserved. Subscriber:
Oxford University Press - Master Gratis Access; date: 09 January 2016
 the International Court of Justice: A Commentary (OUP Oxford 2006) 677–792.
O Corten and P Klein (eds) Les Conventions de Vienne sur le Droit des Traités (Bruylant
Bruxelles 2006).
A Aust Modern Treaty Law and Practice (2nd ed CUP Cambridge 2007).
C Brölmann The Institutional Veil in Public International Law: International Organisations
and the Law of Treaties (Hart Oxford 2007).
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Nijhoff Leiden 2009).
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Oxford 2010).

Select Documents
Aegean Sea Continental Shelf Case (Greece v Turkey) [1978] ICJ Rep 3.
Air Services Agreement of March 27 1946 (United States v France) 18 RIAA 416.
Anglo-Iranian Oil Co (United Kingdom v Iran) (Preliminary Objection) [1952] ICJ Rep 93.
Gabčíkovo-Nagymaros Project (Hungary/Slovakia) [1997] ICJ Rep 7.
Island of Palmas Case (Netherlands v United States of America) (1928) 2 RIAA 829.
Kasikili/Sedudu Island (Botswana/Namibia) [1999] ICJ Rep 1045.
Land and Maritime Boundary between Cameroon and Nigeria (Cameroon v Nigeria:
Equatorial Guinea Intervening) [2002] ICJ Rep 303.
Legal Consequences for States of the Continued Presence of South Africa in Namibia (South
West Africa) notwithstanding Security Council Resolution 276 (1970) (Advisory Opinion)
[1971] ICJ Rep 16.
Maritime Delimitation and Territorial Questions between Qatar and Bahrain (Qatar v
Bahrain) (Jurisdiction and Admissibility) [1994] ICJ Rep 112.
Maritime Delimitation and Territorial Questions between Qatar and Bahrain (Qatar v
Bahrain) (Jurisdiction and Admissibility) [1995] ICJ Rep 6.
Maritime Delimitation and Territorial Questions between Qatar and Bahrain (Qatar v
Bahrain) (Jurisdiction and Admissibility) (Dissenting Opinion of Vice-President Schwebel)
[1995] ICJ Rep 27.
Mavrommatis Palestine Concessions (Greece v Great Britain) (Jurisdiction) PCIJ Series A No
2.
Mavrommatis Palestine Concessions (Greece v Great Britain) (Jurisdiction) (Dissenting
Opinion of Judge Moore) PCIJ Series A No 2.
Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of
America) (Merits) [1986] ICJ Rep 14.
Rainbow Warrior (New Zealand v France) France-New Zealand Arbitration Tribunal (Award of
30 April 1990) 82 ILR 500.
Reservations to the Convention on the Prevention and Punishment of the Crime of
Genocide (Advisory Opinion) [1951] ICJ Rep 15.
Temple of Preah Vihear (Cambodia v Thailand) (Merits) [1962] ICJ Rep 6.
Territorial Dispute (Libyan Arab Jamahiriya/Chad) [1994] ICJ Rep 6.
UN HRC ‘General Comment 24 (Issues Relating to Reservations made upon Ratification or
Accession to the Covenant or the Optional Protocols thereto, or in Relation to Declarations
under Article 41 of the Covenant) (2 November 1994)’ GAOR 50th Session Supp 40, 119 (Vol
I).
Vienna Convention on Succession of States in Respect of Treaties (concluded 23 August
1978, entered into force 6 November 1996) 1946 UNTS 3.
Vienna Convention on the Law of Treaties (concluded 23 May 1969, entered into force 27
January 1980) 1155 UNTS 331.

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 Vienna Convention on the Law of Treaties between States and International Organizations or
between International Organizations (adopted 20 March 1986, not yet in force) (1989) 25 ILM
543.

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