PUBLIC INTERNATIONAL LAW

LAW 207.02 WEEK-II

THE SOURCES OF INTERNATIONAL LAW
DR. DENİZ TEKİN APAYDIN
ARTICLE 38 OF THE STATUTE OF THE ICJ

"1. The Court, whose function is to decide in accordance with international law
such disputes as are submitted to it, shall apply:
a. international conventions, whether general or particular, establishing
rules expressly recognized by the contesting states;
b. international custom, as evidence of a general practice accepted as law;
c. the general principles of law recognized by civilized nations;
d. subject to the provisions of Article 59, [.e. that only the parties bound by the decision in
any particular case,] judicial decisions and the teachings of the most highly qualified
publicists of the various nations, as subsidiary means for the determination of rules of
law”
2.This provision shall not prejudice the power of the Court to decide a case ex aequo et bono, if the
parties agree thereto.”
ARTICLE 38 OF THE STATUTE OF THE ICJ

• Article 38 does not purport to be a list of the sources of international law.

• It is a direction to the ICJ authorising it to consider various materials when
deciding disputes submitted to it.

• Article 38 does not provide a complete list of the matters which the Court
in fact considers when determining the rights and duties of States.
• Ex: Resolutions of UN General Assembly, diplomatic correspondence
 ARTICLE 38 OF THE STATUTE OF THE ICJ

• Article 38 concentrates primarily on the activities of States. However non-State

actors also contribute to law creation.
• International organisations, individuals, groups or multinational companies etc.

• There is no indication in Article 38 of the priority or hierarchy of the sources of

international law.
• Single reference à “subsidiary means” in article 38(1)(d)
 INTERNATIONAL TREATIES

• Treaties are the means by which States can create certain and specific obligations, and
they are usually the outcome of long and difficult negotiations.

• Treaties may be bilateral (between two States) or multilateral (between many).

• Once the treaty has satisfied all the formal requirements for its existence and has entered
into force, it imposes obligations to the State parties which must be carried out.

• The failure to conform to the terms of a binding treaty will incur international
responsibility unless a defense is available.
INTERNATIONAL TREATIES

1) Only parties to the treaty are bound by its terms. There are limited exceptions of this rule :
• Ex : the delimitation of territorial boundaries (erga omnes rule)

2) A State is not bound by a treaty to which it is a party in its relations with a State which is not a
party to the treaty.
• However non-parties to the treaty may come to be bound by customary rules having the same content as
the treaty.

3) When a treaty codifies existing customary law, the substance of the obligations specified in the
treaty may be binding on all States, because;
• Those States that are parties to the treaty are bound by the treaty in the normal way.
• States that are not parties to the treaty cannot be said to be bound by the treaty, but since the treaty
codifies existing customary law, these States are bound by the same obligations as expressed in the treaty.
INTERNATIONAL TREATIES

4) Many multilateral treaties are a mixture of codification of current

customary law and progressive development of that law. In that case;
• Those States that are parties to the treaty are bound by all obligations in the
treaty in the normal way. But non-parties are bound only by those obligations
which have in fact attained the status of customary law.
• This kind of treaties can pave the way for the formation of customary law. If
state practice develops along the lines of the code established by the treaty,
the result can be that new rules of custom come into being. If this happens,
non-parties to the treaty will be bound by the new customary law.
INTERNATIONAL TREATIES

! However, not all treaty provisions can give rise to customary law in this way.
According to ICJ in the North Sea Continental Shelf Cases 1969, in order to extrapolate a general
customary norm from a treaty provision, that treaty provision should be of a fundamentally norm
creating character such as could be regarded as forming the basis of a general rule of law.

The treaty provision which is said to give rise to the custom must be capable of general application
and must be intended to be the basis for future state practice as well as being supported by the
necessary opinio juris and by acts of practice by non-parties to the treaty.

• Contract Treaties à impose obligations

• Law-making Treaties à create law

CUSTOMARY INTERNATIONAL LAW

Customary international law is that law has evolved from the practice or
customs of States. The process of customary law formation is derived from the
practice of States and occasionally the practice of other legal persons. That’s
why international law can develop in line with the needs of the time. à
Flexibility

In the last three decades the treaty has replaced custom as primary source of
international law. à Uncertainty + Lack of Speed in the Development of
New Law
ELEMENTS OF CUSTOMARY INTERNATIONAL LAW

1- State Practice
• Consistency of Practice
• Generality of Practice
• Duration of Practice

2- Opinio Juris
STATE PRACTICE

• State practice includes, but is not limited to;

• Actual activity (acts and omissions)
• Statements made in respect of concrete situations or disputes
• Statements of legal principle made in the abstract (such as those preceding the
adoption of a resolution in the General Assembly)
• National legislation
• The practice of international organisations

• Some scholars argue that any activity of the State can amount to State practice
for the purpose of identifying the content of a legal rule;
• Ex : the Repertory of Practice of UN Organs
CONSISTENCY OF PRACTICE

• The State practice must be reasonably consistent. However there need not be total
consistency, for it is clear that this criterion is satisfied if there is substantial, rather
than complete consistency in the practice of States.

• The degree of consistency may vary according to the subject matter of the rule in
dispute.

• Contrary State practice should, without evidence of greater intent, be presumed to

be action in breach of the rule. This must be correct, for otherwise any State acting
contrary to an existing customary rule, without more, could argue that it was merely
engaged in developing a new rule rather than breaking an existing one.
 GENERALITY OF PRACTICE

• The practice must be common to a significant number of States. However, the practice need only be
“generally adopted in the practice of states” and not all the States need participate before a general
practice can become law.

• The degree of generality may vary according to the subject matter of the rule in dispute.

1- In assessing whether a customary rule has come into existence, special weight may be given to the
practice of those States whose interests are specifically affected by the subject matter of the rule.

2- Persistent Objector: initial and sustained objection will prevent a State being bound by customary rule.

3- Local Custom may exist where a practice has developed between two or more States.
DURATION OF PRACTICE

• The length of time needed will vary from subject to subject.

• Instant custom is a possibility, however, it would require very

strong evidence that States regarded the new “practice” as
legally binding.
OPINIO JURIS

• States must recognise the rule as binding upon them as law. State practice must be
accompanied by a belief that the practice is obligatory, rather than merely convenient or
habitual.

• The same State activity may be evidence of a general, uniform and consistent State
practice as well as the evidence of opinio juris necessary to turn that practice into law.

• Indeed, opinio juris may be demonstrated “by induction based on the analysis of a
sufficiently extensive and convincing practice”. (Delimitation of the Maritime Boundary
in the Gulf of Maine Area (Canada/United States of America) 1984, para. 111; Question
of the Delimitation of the Continental Shelf Between Nicaragua and Colombia Beyond
200 Nautical Miles From The Nicaraguan Coast (Nicaragua/Columbia) 2023, para.77.)
 HOW DOES CUSTOMARY LAW CHANGE?

Breach of customary international law or Change of customary international law?

In such cases, opinio juris will play a pivotal role : in particular, the manner in
which the contrary conduct is received by interest of members of the international
community and any applicable judgment of the ICJ or other international judicial
body.

Continued and sustained criticism of the contrary conduct is clear evidence that
no replacement rule of customary law is emerging.
CUSTOMARY INTERNATIONAL LAW

1- Even if the contrary conduct has not been accepted by the international
community at large, a State which accepts or acquiesces in the conduct of
another State that is ostensibly in breach of an existing customary norm,
will be taken to have forfeited the right to complain of the breach.

2- It will be very difficult to establish that a rule of jus cogens has been
changed by contrary State practice. (Rules of jus cogens are fundamental
rules that not even a treaty can contradict.)
THE RELATIONSHIP BETWEEN CUSTOMARY LAW
AND TREATY LAW
Where custom and treaty are COMPLEMENTARY

Where customary law and treaty law stipulate the same or similar legal
obligations there are few problems :

Parties to the treaty will be bound by the treaty and non-parties will be bound
by custom.

Parallel obligation for parties to the treaties!

 THE RELATIONSHIP BETWEEN CUSTOMARY LAW
AND TREATY LAW
When custom and treaty CONFLICT

1- If the treaty is later in time than the custom, the treaty will prevail. (lex posterior derogat legi
priori)

2- Where contrary customary law has developed subsequent to the adoption of a treaty, the
treaty continues to govern the relations between the parties even though a new practice has
developed.

3- Any treaty provision which conflicts with a rule of jus cogens is void and this is true whether
or not the rule of jus cogens developed before or after the treaty came into force.
GENERAL PRINCIPLES OF LAW

Included in the list of sources of international law in Article 38 of the

International Court of Justice Statute are “general principles of law
recognized by civilized nations”

Ex: laches, good faith, res judicata, and the impartiality of judges.

International tribunals rely on these principles when they cannot find

authority in other sources of international law.
OTHER SOURCES

• Judicial Decisions
• ICJ and other international courts/tribunals

• Writings of Publicists

• Unilateral Statements by States

• Declaration, condemnation, recognition, promise…

• Resolutions and Decisions of International Organizations

• UN General Assembly, UN Security Council …