1.

Nature and Development of International Law

1.1 Definition of International Law

International law is the set of rules and principles governing how sovereign states interact with
each other and with international organizations and individuals. It covers issues like war, human
rights, trade, diplomacy and the environment. In practice, international law relies on consent of

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states (for example, through treaties) and institutions like the UN to create and enforce its rules.

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Its goal is to promote peace, order and cooperation among nations.

1.2 Development of International Law

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●​ Peace and Security: After the devastation of World War II, the need for peace led states
to build a stronger international order. In 1945 they created the United Nations (UN)
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with a Charter aiming to prevent war and maintain peace. The UN Charter’s powers (e.g.
the Security Council’s ability to act for peace) have guided development of international
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law on force and security.​

●​ Human Rights Generations: After WWII, states also began expanding human rights
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law. The 1948 Universal Declaration of Human Rights (UDHR) began civil and political
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rights (1st generation), then economic/social/cultural rights were added by 1966

covenants (2nd generation), and later collective rights like development, environment
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and self-determination (3rd generation) were recognized. UN bodies and treaties now
protect these rights worldwide.​
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●​ International Law Commission (ILC): The UN created the ILC in 1947 to codify and
develop international law. The ILC studies topics and drafts model rules and
conventions (e.g. on treaties, state responsibility, law of the sea) for UN adoption. Its
work helps turn customary practices into written treaties and clarifies rules (e.g. the
Vienna Convention on Treaties was based on ILC work).​
1.3 Codification – Work of the ILC

The ILC’s mandate is to "encourage the progressive development of international law and its
codification". It chooses topics (like diplomatic law, human rights, treaties, responsibility) and
produces draft articles and conventions. For example, the Vienna Conventions on treaties and
on diplomatic relations originated from ILC drafts. Through international conferences and UN
negotiation, many ILC proposals become binding conventions, putting into writing what once
was only customary (practice-based) law. This codification makes rules clearer and more

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accessible to all countries.

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1.4 Sanctions and Enforcement Mechanisms

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While international law has no single global enforcer, it has several means of enforcement:

●​ UN Security Council: Under Chapter VII of the UN Charter, the Security Council can
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impose binding measures (often called “sanctions”) to maintain peace. It may enact arms
embargoes, economic sanctions, travel bans or authorize force. (Article 41 lists non-force
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sanctions.)​

●​ UN General Assembly: GA resolutions are generally recommendatory (non-binding),

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but they can reflect global consensus. For example, the GA asked the ICJ for advisory
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opinions (e.g. on nuclear weapons) to clarify legal questions. GA also passed historical
resolutions like the 1974 New International Economic Order declaration for a fairer
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global economy.​

●​ International Court of Justice (ICJ): The ICJ issues binding judgments between
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states that consent to its jurisdiction. All UN members “undertake to comply” with ICJ
decisions. If a losing state does not obey, the other party can take the matter back to the
Security Council, which may recommend measures. The ICJ can also indicate provisional
measures (urgent orders) to protect rights during a case.​

●​ Other Judicial Bodies: Specialized tribunals like the International Tribunal for the
Law of the Sea (ITLOS), International Criminal Court (ICC), and arbitral forums
 like the Permanent Court of Arbitration (PCA) also issue binding decisions. For
example, the ICC prosecutes individuals for crimes like genocide and war crimes; the
PCA facilitates arbitration between states; ITLOS decides maritime disputes.​

●​ Human Rights Bodies: Under human rights treaties, monitoring committees (e.g. UN
Human Rights Committee) can issue findings. Though not “sanctions” in the usual sense,
these bodies can “name and shame” violators or recommend reparations. Some treaties

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allow individuals to petition international courts (e.g. European Court of Human Rights,
Inter-American Court) for binding judgments.​

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1.5 Subjects of International Law

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The main subjects (holders of rights and duties) are:
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●​ States: Traditional primary subjects. States have territory, population and government.
Only states can make treaties and vote at the UN.​
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●​ International Organizations: Entities like the UN, EU, World Bank, WHO etc. They
have international legal personality in areas given by their founding charters. They can
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enter treaties, bring claims (through states or on own behalf) and have limited
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rights/duties.​
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●​ Individuals: Individuals also have international rights and duties. For example, people
have human rights protected by treaties, and individuals can be held criminally
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responsible by tribunals (like the ICC). However, individuals do not generally make
treaties or claim state-like rights.​

Case: Reparation for Injuries Suffered in the Service of the United Nations (1949) – Facts:
UN Mediator Count Bernadotte was assassinated in 1948 while on a UN peace mission. The UN
General Assembly asked the ICJ whether the UN (not a state) could bring an international claim
against the responsible state for damages. Issue: Does the UN have legal capacity/personality to
claim reparation? Judgment: The Court held yes. It stated the UN was intended to have “a large
measure of international personality” to fulfill its duties. Thus the UN could claim compensation
not only for damage to itself but also for the victim’s losses. This confirmed that the UN is an
international legal subject with rights under international law.

Case: Ukraine v. Russia (Financing of Terrorism & Racial Discrimination), ICJ (2024) –
Facts: Ukraine sued Russia under two treaties: the Anti-Terrorism Financing Convention
(ICSFT) and the Racial Discrimination Convention (CERD). Ukraine accused Russia of failing

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to stop funds reaching armed groups in eastern Ukraine (2014-present) and of discriminating

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against Crimean Tatars and Ukrainians in Crimea. Issues: Did Russia breach its ICSFT duty (to
prevent and prosecute terrorism financing) and its CERD duty (to protect minorities)? Judgment:
The ICJ found that Russia violated Article 9(1) of the ICSFT by failing to fully cooperate and

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investigate Ukraine’s terrorism financing allegations. (Article 9(1) requires mutual legal
assistance.) However, Ukraine’s other ICSFT claims were not upheld because Ukraine had not
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shown clear evidence of violations, and the Court noted Russia had no duty to label groups as
terrorists without grounds. On CERD, the Court concluded no violation was established. It
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found insufficient proof that Russia’s actions against Crimean Tatars or measures like banning
the Tatar assembly (Mejlis) were motivated by ethnic discrimination. In short, the Court declared
Russia must investigate alleged terrorism financing (ICSFT art. 9), but dismissed Ukraine’s
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racial discrimination claims (no proven breach of CERD).

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1.6 Third World and International Law

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Many newly independent developing (Third World) states after 1945 saw international law as
biased toward colonial powers. They pushed for reforms. For instance, in 1974 the UN General
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Assembly adopted a New International Economic Order (NIEO), reflecting developing

countries’ demands for a fairer global economy. Academics also formed TWAIL (Third World
Approaches to International Law) to critique traditional IL as perpetuating inequality. TWAIL
scholars argue IL was shaped by colonialism and call for it to better serve formerly colonized
nations. This Third World perspective emphasizes sovereignty, non-intervention and
self-determination. Over time, decolonization and developing-state activism (e.g. NAM
movement, GA voting) have led to new treaties and norms (like additional human rights treaties)
that reflect these concerns.

2. Sources of International Law

2.1 Article 38 of the ICJ Statute

Article 38(1) of the ICJ Statute is a classic list of IL sources. It directs courts to apply:

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●​ Treaties (international conventions): Written agreements between states (bilateral or

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multilateral). Treaties may be general (open to all, like the UN Charter) or special. They
create clear legal obligations for parties.​

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●​ Customary international law: Practices consistently followed by states out of a sense of
legal duty (opinio juris). Customary rules may come from long-standing state practice
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(e.g. law of the sea, diplomatic immunity) and bind all states, not just treaty parties. The
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Court looks for widespread, uniform practice plus belief it’s obligatory (see cases below).​

●​ General principles of law: Fundamental principles common to major legal systems (like
good faith, estoppel, res judicata, equality before the law). These fill gaps in
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treaties/customs. For example, the ICJ recognized the principle that “agreements must be
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kept” (pacta sunt servanda) and the need for honest fulfillment of obligations.​
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●​ Judicial decisions and scholarly writings: Previous PCIJ/ICJ judgments and the
teachings of respected jurists are subsidiary sources. They guide the Court by analogy,
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but are not binding precedents (Article 59 makes only the case parties bound by a
judgment). Well-known decisions (like Lotus or Asylum) and textbooks are often cited to
clarify legal rules.​

●​ Ex aequo et bono: Article 38(2) allows the ICJ to decide a case on equitable terms
(fairness) if the parties agree. In practice this is rare; normally the Court bases decisions
on the above sources. Ex aequo et bono essentially means “according to what is fair and
 good,” bypassing strict legal rules if both sides consent.​

2.1.1 International Treaties and Conventions

Treaties (also called conventions) are written agreements that explicitly create rules. Examples
include the Charter of the UN, the Vienna Convention on Treaties (1969), and human rights
treaties (like the ICCPR, CEDAW). These are binding on signatory states under the principle

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pacta sunt servanda (agreements must be kept). Courts give effect to clear treaty texts.

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2.1.2 International Custom

Custom is unwritten law formed by consistent state practice plus opinio juris (belief that the

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practice is legally required). It is demonstrated by many states acting in a certain way. Key cases:

●​ Lotus (France v. Turkey, PCIJ 1927) – Facts: A French ship (Lotus) collided with a
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Turkish ship; a Turkish sailor died. France claimed that only French courts had
jurisdiction over their officer. Issue: Could Turkey prosecute the French officer for the
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incident on the high seas? Judgment: The Court held yes. It established the “Lotus
principle”: states may exercise jurisdiction over conduct on the high seas unless an
international rule expressly prohibits it. Because no treaty or custom banned Turkey’s
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action, both Turkey and France had concurrent jurisdiction. This meant Turkey did not
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violate international law. The Lotus case illustrates that a permissive or prohibitive rule
must exist for jurisdiction; silence in the law means a state is free to act. .​
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●​ North Sea Continental Shelf (1969) – In disputes over continental shelf borders, Germany
argued for a custom requiring median lines. The ICJ famously held that to prove a
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customary rule (like a fixed boundary method), states must show widespread and
representative practice, done out of legal obligation. Finding no such uniform practice,
the Court said no binding custom on shelf delimitation existed. Thus no automatic
equidistance rule applied, and boundaries were to be negotiated. (This case highlights the
high threshold for proving custom.)​
 ●​ Right of Passage (Portugal v. India, ICJ 1960) – Facts: Portugal’s enclaves (Dadra and
Nagar Haveli) in India claimed a historic right-of-passage through Indian territory. India
had long regulated this access. Issue: Did a customary right-of-passage exist requiring
India to allow unrestricted transit? Judgment: The Court found Portugal did have a
right-of-passage in 1954, but only by agreement (not a general custom). It held the
right was limited (no military or arms). India was not in breach as it did not violate the
terms of that right. This case shows the Court will look at treaties and local practice to

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determine if a custom exists, and will enforce only the right actually recognized by prior
practice.​

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●​ Asylum (Colombia v. Peru, ICJ 1950) – Although primarily treaty interpretation, it

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touched on custom: Peru argued regional custom on diplomatic asylum. The ICJ noted
that neither general nor regional custom supported Peru’s position. In short, customary
law requires evidence of consistent state practice and belief in its legality, and partial
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or inconsistent practices do not create a binding rule.​
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2.1.3 General Principles of Law

These are fundamental rules common to legal systems worldwide. For instance: good faith
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(states must honor their obligations honestly), estoppel (a state can’t go back on its word if
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another relied on it), and proportionality. Important cases:

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●​ Effect of Awards (UN Admin. Trib., ICJ 1954) – Though not a substantive dispute, the
Court applied pacta sunt servanda. It found that awards by the UN’s administrative
tribunal were binding: the UN General Assembly could not refuse to implement a
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compensation award to an official. The tribunal was “independent and truly judicial” and
its judgments “were therefore binding on the United Nations”. This relied on the general
principle that legal agreements and final judicial decisions must be honored.​

●​ Island of Palmas (Netherlands v. USA, PCA 1928) – Facts: Competing claims over
Palmas Island (Indonesia) by the Dutch and the US (the latter inherited Spanish claim).
 Issue: What determines sovereignty? Finding: The arbitrator (not ICJ, but a classic
reference) held that sovereignty rests on effective, continuous display of authority
(administration, sovereignty acts). Discovery alone does not suffice; actual control does.
This is a general principle for territorial title.​

●​ Preah Vihear (Cambodia v. Thailand, ICJ 1962) – Facts: Dispute over border near the
Preah Vihear temple. A 1904 treaty specified the watershed as border, and a 1939 map

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showed the temple in Cambodia. Thailand later disputed the map’s validity. Issue: Did
Thailand’s later objections negate the map? Judgment: The Court found Thailand had

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accepted the 1939 map, confirming the temple lay in Cambodia. This was based on the
principle of acquiescence – by accepting the map for decades, Thailand was bound by it.

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The Court then held Thailand must withdraw its troops. This case applied general
principles like good faith and honoring agreed boundaries.​
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2.1.4 Judicial Decisions and Juristic Writings
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Article 38 lists ICJ/PCIJ decisions and writings of scholars as subsidiary means. In practice, the
Court often cites past cases or legal literature for guidance. However, no case (except on consent)
is automatically binding. The Court tries to maintain consistency by following its own prior
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judgments, but it is free to distinguish them. Authoritative commentaries (like Oppenheim’s or

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Anzilotti’s) are also used to explain principles.

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2.1.5 Ex aequo et bono

This Latin phrase means “according to what is fair and equitable.” Article 38(2) allows the ICJ to
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decide a dispute on equitable grounds (not strictly by law) if both parties agree. In other words,
the Court can tailor justice without being bound by strict legal rules, but only with consent. This
is rarely done; states usually prefer the Court to apply legal norms.

2.2 Other Sources of International Law

2.2.1 UN General Assembly Resolutions

UNGA resolutions (except under rare “Uniting for Peace” cases) are recommendations and not
binding law. However, they can reflect international consensus or interpret law. For example, GA
49/75 K (1994) asked the ICJ for an advisory opinion on nuclear weapons. In that 1996 advisory
opinion, the Court considered applicable law (UN Charter, humanitarian law) and noted no
explicit authorization of nuclear use. It found no single rule outrightly banned nuclear weapons
use, but their use must comply with humanitarian law in each case. This case shows GA can
refer legal questions to the ICJ, and the Court will then examine treaties, customs, and principles

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(not the GA resolution itself as law).

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2.2.2 UN Security Council Resolutions

SC resolutions adopted under Chapter VII of the UN Charter create binding obligations for UN

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members (Article 25). For example, in Namibia (Advisory Opinion 1971), the Court held that
Security Council resolutions (276) declaring South Africa’s presence in Namibia illegal were
obligations binding on all states. It said the UN’s decision to terminate the Mandate and declare
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illegality was “opposable to all States,” barring them from recognizing any acts by South Africa
in Namibia.
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Similarly, in Western Sahara (1975), requested by the GA, the Court emphasized the binding
force of earlier UN resolutions. It affirmed that decolonization rules (GA Res. 1514 (1960) –
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self-determination) applied fully to Western Sahara. The Court also noted that UN personnel
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were under UN authority, reinforcing respect for SC/GA measures.

In Kosovo (Advisory 2010), the Court considered SC Resolution 1244 (1999) which had placed
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Kosovo under UN administration. The Court held Kosovo’s 2008 declaration of independence
did not violate that resolution. It found 1244 created an interim regime and did not prohibit a
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unilateral declaration by representatives of the people of Kosovo. The authors of the declaration
acted outside the Provisional Institutions, so they were not bound by their limited powers. Thus,
while SC resolutions under Chapter VII are law, this case shows the Court will interpret their
scope carefully when advising on compliance.

2.2.3 Other Advisory Opinions (PCIJ/ICJ)

Advisory opinions by the International Court (or its predecessor PCIJ) are not binding law but
carry great authority. States and UN bodies seek them for guidance on international legal
questions. A recent example is the Chagos Archipelago advisory opinion (2019). The General
Assembly asked whether the separation of the Chagos Islands from Mauritius in 1965 was
lawful, given self-determination obligations. The ICJ advised that decolonization of Mauritius
was not lawfully completed due to this detachment, and that the UK must end its administration
of Chagos as soon as possible. The Court based this on the right to self-determination and

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relevant UN resolutions. Although advisory, this opinion is influential: it confirms that opinions,
resolutions and practices in decolonization carry legal weight and that certain colonial acts (like

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splitting a colony) violated international law.

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