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Public International Law: Sources

Guidance for researching subjects related to public international law.

Sources of International Law

Article 38 of the Statute of the International Court of Justice, the judicial body of the United Nations, is widely considered to identify the sources of international law: 

1. The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:

a. international conventions [treaties], whether general or particular, establishing rules expressly recognized by the contesting states;

b. international custom, as evidence of a general practice accepted as law;

c. the general principles of law recognized by civilized nations;

d. 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. [These particular sources, including previous decisions of the ICJ, are non-binding.]

2. This provision shall not prejudice the power of the Court to decide a case ex aequo et bono [in equity], if the parties agree thereto.

Statute of the International Court of Justice art. 38, June 26, 1945, 59 Stat. 1031.

This guide contains sources and further guidance for finding/researching these areas of law. 

For General Reference

For introductory information, use this book: Marci B. Hoffman & Robert C. Berring, International Legal Research in a Nutshell (2017). The book discusses much of what we will cover here but in a much more in-depth manner.

For lists of resources (including URLs!) and more up-to-date information, use this book: George Wash. Int’l Law Review, Guide to International Legal Research (2019). The introduction provides an overview of sources of international law, including the traditional sources like conventions and customs, while introducing the influence of municipal courts and soft law. Chapters are arranged by geographic region – like South Asia and the Middle East – and by subject – like intellectual property and maritime law. Also available on Lexis.

Note on Citations

If it is important to cite to the Bluebook for your research, remember that the Bluebook has preferred sources. This is true for international and national (domestic and foreign) cases, treaties, and other documents of international organizations. If you have any questions about official/authentic documents and citing in accordance with the Bluebook, please see a reference librarian - do not struggle by yourself. 

Citations to international and foreign sources can be incredibly confusing. In the Bluebook, be sure to read the entirety of Rules 20 (Foreign Materials) and 21 (International Materials) in conjunction with their relevant tables in T1, T2, and T3. You may also wish to consult N.Y. Univ. Sch. of Law Journal of Int’l Law & Politics, Guide to Foreign and International Legal Citations (2nd ed. 2009). K89 .G85 2009 (reference).

Historical Resources - Understanding the History of International Law


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