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Public International Law

A guide to resources for public international law research, created by John Bolan, Bora Laskin Law Library

Sources of International Law

Article 38(1) of the International Court of Justice (ICJ) Statute is generally considered to be the most authoritative enumeration of the sources of International law (Thomas Buergenthal & Sean  Murphy, Public International Law in a Nutshell) Although it is no longer thought to be a complete enumeration of the sources of international law, it remains the best starting point.


Article 38(1) lists the sources of international law as:


  • a) International conventions (treaties);

  • b) International custom (general practice of states and intergovernmental institutions that are legally binding and generally recognized by all states);

  • c) General principles of law; and

  • d) Judicial decisions and scholarly "teachings" as a “subsidiary means for the determination of rules of law”.

Other Sources of International Law

Aside from the sources outlined in s. 38(1), there is significant scholarly discussion on other sources of international law such as ‘soft law’, unilateral declarations, principles of equity, and the secondary law of IGOs for example. For more on this topic see any of these  the treatises listed in the 'books' tab of this guide. For a collection of articles on this topic see Martti Koskenniemi, ed., Sources of International law




More on article 38

  • It is generally accepted that the sources in Article 38 are listed in order of importance.
  • Many scholars consider the sources in d) to be secondary sources, as they are a “subsidiary means” of determining the law.