International Law Research Guide

About the Sources of International Law

The International Court of Justice (ICJ) identifies the sources of international law in the

Article 38 which reads:

  1. The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:
    1. international conventions, whether general or particular, establishing rules expressly recognized by the contesting states;
    2. international custom, as evidence of a general practice accepted as law;
    3. the general principles of law recognized by civilized nations;
    4. subject to the provisions of Article 59, 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.

 

According to this statute, the primary sources you will use are:
  • Treaties (AKA international conventions)
  • Customary International Law (State practice combined with opinio juris)
  • General Principles of Law
  • Writings of Publicists
  • Judicial Decisions
  • Soft Law/Non-Legally Binding Instruments

Videos and Articles that Explain the Key Concepts of Sources of International Law.

UN Audiovisual Library of International Law
The Law Academy

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Articles:

Books

Sources of International Law Theory

Finding Sources of International Law

To Find Treaties use:
To find Customary International Law (State practice combined with opinio juris), use
To Find General Principles of Law:

General principles can be determined from reliable secondary sources on foreign law. This is an exercise in comparing laws from different jurisdictions and looking for similarities.

To Find Writings of Publicists:
To Find Judicial Decisions:
To Find Soft Law/Non-Legally Binding Instruments: