Sources: Article 38 of the ICJ Statute

International Law · Nature and sources. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

Article 38(1) of the Statute of the International Court of Justice is the accepted list of sources. The Court applies treaties, international custom and the general principles of law recognised by civilised nations. Judicial decisions and the writings of the most highly qualified publicists are only subsidiary means of finding the law.

Custom needs two things together: a general and consistent practice of states, and opinio juris, the belief that the practice is required by law. Practice followed only from courtesy or habit is not custom. A state that objects clearly and consistently while a rule is still forming, a persistent objector, is in general not bound by it.

Rules to remember

Article 38(1)(a) treaties; (b) custom; (c) general principles of law; (d) judicial decisions and teachings of publicists as subsidiary means.
Article 38(2): the Court may decide ex aequo et bono (by fairness) only if the parties agree.
Article 59: a decision binds only the parties and only in that case, so there is no binding precedent.
Custom = state practice + opinio juris sive necessitatis.
North Sea Continental Shelf cases (1969): practice must be extensive and virtually uniform, with a sense of legal duty.
Asylum case (1950): a regional custom must be constant and uniform; Colombia's claim failed.
Anglo-Norwegian Fisheries case (1951): the authority usually cited for the persistent objector.

Common mistake

General Assembly resolutions are not listed in Article 38(1) and are not binding sources in themselves; they may only be evidence of practice or opinio juris. Also, judicial decisions are subsidiary means, not a main source.

Worked example

For many years most states have sent messages of sympathy when a foreign head of state dies. A state that sends none is accused of breaking customary law. Is the accusation sound?

Custom needs two elements: general state practice and opinio juris.
The practice exists, since most states send such messages.
States send them out of courtesy (comity), not because they believe the law requires it, so opinio juris is missing.

Answer: No. The practice is a usage of courtesy, not a rule of customary international law.

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