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Public International Law

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

Research Strategy

  1. Start with books and articles that address customary law in the area that you are researching.
  2. The secondary sources will provide you with citations to the sources they rely.
  3. Follow those citations to the primary sources.

International Custom - Article 38(1)(b)

Customary international law and general principles of law are challenging to research because they are documented in a wide variety of sources.  Researchers unfamiliar with the area should consult one of the general works on international law listed in the 'Books' tab, or consult one of the resources listed on this page to gain an understanding of the general principles before proceeding to more specific research.


The elements of customary international law include:

1. Widespread repetition by States of similar international acts over time (State practice).
2. Acts must occur out of sense of obligation (opinio juris). 
3. Acts must be taken by a significant number of States and not be rejected by a significant number of States.

For information on customary international law see the resources listed below, or the relevant chapters in the treatises listed in the books tab

Research guides to Customary Law

Scholarly discussions of Customary Law