Article 38 of the ICJ Statute

Article 38 of the Statute of the International Court of Justice is one of the most important provisions in Public International Law. It identifies the principal sources and subsidiary means that the Court applies when deciding disputes submitted to it. It is therefore central to the study of the sources of international law.

Article 38 distinguishes between international conventions, international custom and general principles of law as the principal legal materials, while judicial decisions and juristic writings are treated as subsidiary means for determining rules of law.

Text and Structure of Article 38

Article 38(1) provides that the Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:

Article 38(1)(a)

International conventions, whether general or particular, establishing rules expressly recognised by the contesting States.

Article 38(1)(b)

International custom, as evidence of a general practice accepted as law.

Article 38(1)(c)

The general principles of law recognised.

Article 38(1)(d)

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.

Article 38(2) further provides that the Court may decide a case ex aequo et bono, or according to what is fair and equitable, if the parties agree.

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Purpose of Article 38

Article 38 primarily performs two functions:

1. It identifies the legal materials that the ICJ applies when deciding disputes.
2. It provides a framework for identifying and determining rules of international law.

It is therefore frequently described as the principal provision concerning the sources of international law.

However, Article 38 should not be understood as a complete legislative code of every possible source of international law. International law has developed significantly since the Statute was drafted, including through the practice of international organisations and other developments.

Article 38(1)(a) – International Conventions

International conventions, commonly called treaties, are the first category identified by Article 38.

A treaty is an international agreement governed by international law that creates rights and obligations for its parties.

Treaties may be:

• bilateral;
• multilateral;
• general;
• particular;
• regional;
• specialised.

Importance

Treaties provide an express and formal method through which States establish legal obligations.

They are particularly important in areas such as:

• human rights;
• diplomatic relations;
• international trade;
• environmental protection;
• law of the sea;
• international criminal cooperation.

Example

The Vienna Convention on the Law of Treaties provides an extensive framework governing treaty relations.

Article 38(1)(b) – International Custom

International custom is the second principal category.

Article 38(1)(b) defines it as:

“international custom, as evidence of a general practice accepted as law.”

Custom traditionally requires two elements:

1. State Practice

There must be sufficiently general and consistent practice by States.

2. Opinio Juris

States must follow the practice because they regard it as legally required or legally permitted.

Therefore:

State Practice + Opinio Juris = Customary International Law

Examples

Customary rules may concern:

• diplomatic immunity;
• prohibition of genocide;
• prohibition of aggression;
• principles of State responsibility;
• certain rules concerning the use of force.

The precise customary status of any particular rule must be determined by examining the relevant practice and legal belief.

Article 38(1)(c) – General Principles of Law

The third category is general principles of law.

These are generally understood as fundamental legal principles recognised across legal systems and capable of application within the international legal order.

They may help:

• fill gaps;
• support judicial reasoning;
• interpret legal rules;
• resolve procedural questions.

Examples include principles concerning:

• good faith;
• res judicata;
• estoppel;
• reparation;
• procedural fairness.

General principles are distinct from customary international law because they are not established through the same State-practice-and-opinio-juris test.

Article 38(1)(d) – Judicial Decisions

Judicial decisions are described as subsidiary means for determining rules of law.

They include decisions of:

• International Court of Justice;
• Permanent Court of International Justice;
• international tribunals;
• arbitral tribunals;
• relevant national courts.

Judicial decisions can help:

• interpret treaties;
• identify customary rules;
• apply general principles;
• clarify legal concepts.

However, judicial decisions do not generally constitute universally binding precedent.

Article 59

Article 59 of the ICJ Statute provides that an ICJ decision has binding force only between the parties and in respect of that particular case.

Therefore:

An ICJ judgment is binding on the parties to the case but is not generally binding precedent for every State.

Article 38(1)(d) – Juristic Writings

Article 38(1)(d) also recognises the teachings of the most highly qualified publicists as subsidiary means.

Juristic writings include:

• textbooks;
• treatises;
• scholarly articles;
• commentaries;
• expert legal studies.

They help:

• explain complex rules;
• identify State practice;
• analyse judicial decisions;
• trace the historical development of international law;
• clarify competing interpretations.

They are persuasive rather than binding.

Article 38(2) – Ex Aequo et Bono

Article 38(2) provides an exceptional possibility for the Court to decide a dispute ex aequo et bono, meaning broadly according to considerations of fairness and equity.

However, this can occur only if the parties agree.

This is important because the ICJ cannot ordinarily disregard applicable international law simply because it considers another outcome fairer.

Classification of Article 38

Provision	Legal Material	Nature
Article 38(1)(a)	International conventions	Principal source
Article 38(1)(b)	International custom	Principal source
Article 38(1)(c)	General principles of law	Principal source
Article 38(1)(d)	Judicial decisions	Subsidiary means
Article 38(1)(d)	Juristic writings	Subsidiary means
Article 38(2)	Ex aequo et bono	Available only with consent of parties

Are Article 38 Sources Hierarchical?

Article 38 does not expressly establish a strict hierarchy among treaties, custom and general principles.

However, conflicts between different rules may be governed by other principles of international law.

For example:

• a treaty may govern relations between its parties;
• customary rules may continue to operate alongside treaties;
• jus cogens norms have a special superior status.

Therefore, Article 38 should not simply be interpreted as a rigid ranking of sources.

Article 38 and Treaties vs Custom

Treaties and customary international law can coexist.

A treaty may:

• codify existing custom;
• crystallise an emerging customary rule;
• contribute to the development of custom;
• establish treaty obligations applicable specifically to its parties.

A customary rule can also exist independently of a treaty.

The Nicaragua v. United States case is particularly important for understanding this relationship.

Article 38 and Jus Cogens

Jus cogens is not expressly listed as a separate category in Article 38.

However, modern international law recognises peremptory norms of general international law as having a special status.

A jus cogens norm cannot be displaced by an ordinary treaty.

Therefore, Article 38 must be understood in the context of the broader development of international law.

Article 38 and International Organisations

International organisations are not expressly listed as a separate source in Article 38.

Nevertheless, their activities can have legal significance.

For example:

• UN resolutions may provide evidence of opinio juris;
• organisational practice may contribute to legal development;
• Security Council decisions may be binding where authorised by the UN Charter;
• international organisations may facilitate treaty-making and codification.

Thus, modern international law has developed beyond a simplistic reading of Article 38 as an exhaustive list.

Important Cases

North Sea Continental Shelf Cases, 1969

The ICJ examined the formation of customary international law and emphasised the importance of:

• State practice;
• consistency of practice;
• opinio juris.

The case is fundamental to Article 38(1)(b).

Nicaragua v. United States, 1986

The ICJ considered customary international law alongside treaty obligations.

The case demonstrated that customary rules can operate independently of treaty provisions.

Chorzów Factory Case, 1928

The Permanent Court of International Justice developed the principle of full reparation for internationally wrongful acts.

The case is important in understanding the development and application of general legal principles and State responsibility.

Asylum Case, 1950

The ICJ considered the existence of an alleged regional customary rule.

The case is particularly relevant to the requirements for establishing customary international law.

Barcelona Traction, 1970

The ICJ discussed obligations owed to the international community as a whole and contributed to the development of the concept of erga omnes obligations.

Importance of Article 38

Article 38 is important because it provides a basic framework for understanding where international legal rules come from.

It helps identify:

Treaty Law

Express international agreements.

Customary Law

General State practice accepted as law.

General Principles

Fundamental legal principles capable of international application.

Subsidiary Means

Judicial decisions and juristic writings that help determine and explain legal rules.

Common Confusions

Is Article 38 itself a source of international law?

Not exactly.

Article 38 is a provision of the ICJ Statute that identifies the legal materials the Court applies in deciding disputes.

Does Article 38 contain an exhaustive list of all modern sources?

Not necessarily.

International law has developed through international organisations, institutional practice and other processes that are not neatly captured as separate categories in Article 38.

Are judicial decisions binding on all States?

No.

Under Article 59, ICJ judgments are binding only between the parties and in respect of the particular case.

Is a treaty always superior to custom?

No.

There is no simple universal hierarchy between treaty law and customary law. The applicable rule depends upon the circumstances and other principles of international law.

Is every international practice customary international law?

No.

Custom requires general and sufficiently consistent State practice accompanied by opinio juris.

Are juristic writings legally binding?

No.

They are subsidiary and persuasive materials.

Can the ICJ decide according to equity?

Only if the parties agree to an ex aequo et bono determination under Article 38(2).

Article 38 and Sources of International Law

Source / Material	Article	Key Feature
Treaties	38(1)(a)	Express international agreement
Custom	38(1)(b)	General practice accepted as law
General principles	38(1)(c)	Fundamental principles recognised across legal systems
Judicial decisions	38(1)(d)	Subsidiary means
Juristic writings	38(1)(d)	Subsidiary means
Ex aequo et bono	38(2)	Requires consent of parties

Quick Revision

• Article 38 of the ICJ Statute is central to the study of the sources of international law.
• Article 38(1)(a) deals with international conventions or treaties.
• Article 38(1)(b) deals with international custom.
• Custom requires:
  • State practice;
  • opinio juris.
• Article 38(1)(c) deals with general principles of law.
• Article 38(1)(d) identifies:
  • judicial decisions;
  • teachings of highly qualified publicists.
• Judicial decisions and juristic writings are subsidiary means, not generally primary sources.
• Article 59 limits the binding force of ICJ judgments to the parties and particular case.
• Article 38(2) permits an ex aequo et bono decision only when the parties agree.
• Article 38 does not establish a simple rigid hierarchy between treaties, custom and general principles.
• Modern international law has developed beyond a narrow interpretation of Article 38 through international organisations, institutional practice and other developments.
• North Sea Continental Shelf is important for custom.
• Nicaragua v. United States is important for the relationship between treaties and custom.
• Chorzów Factory is important for reparation.
• Asylum is important for regional custom.
• Barcelona Traction is important for erga omnes obligations.

Conclusion

Article 38 of the ICJ Statute provides the fundamental framework for studying the sources and subsidiary means of Public International Law. It identifies treaties, customary international law and general principles of law as the principal legal materials applied by the Court, while judicial decisions and juristic writings operate as subsidiary means for determining rules of law. Article 38(2) additionally permits the Court to decide a dispute ex aequo et bono where the parties agree. Although Article 38 remains the starting point for understanding the sources of international law, the modern international legal system has developed considerably through international organisations, institutional practice, codification and other legal processes. It should therefore be treated as a foundational framework rather than a rigid and exhaustive catalogue of every form of international legal development.