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International Law: Home

This guide provides a general introduction to international legal research, including secondary sources and current awareness tools. For more extensive research guidance, consult the Law Library's guides listed on the FCIL Guides tab.

What is International Law?

International law is the law among and between nations, such as treaties. In contrast, Foreign law involves the law of jurisdictions outside of the United States, such as the law of France or Brazil. Comparative law studies the differences and similarities of the laws and legal traditions of different countries. The acronym FCIL is sometimes used to to refer to foreign, comparative and international law collectively.

There are two sides of international law: public and private. Public international law involves the law regulating the relations of states; it is often simply called "international law."  Private international law involves the law regulating the behavior of individuals crossing national boundaries. There is another guide which specifically deals with the resources for private international law (linked under the FCIL Guides tab).

Sources of International Law

The International Law Guide provides a starting point for your research of international law. The guide provides sources for researching specific International Law subject areas as well as the basic sources of international law.  The Statute of the International Court of Justice sets out the four sources of international law considered by the ICJ in Art. 38:

  • international conventions, whether general or particular, establishing rules expressly recognized by the contesting states;
  • international custom, as evidence of a general practice accepted as law;
  • the general principles of law recognized by civilized nations;
  • 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

Sources of International Law

Mr. Anthony D’Amato
Judd and Mary Morris Leighton Professor of Law
Northwestern University School of Law

What is General International Law

Mr. Christian Tomuschat
Professor emeritus 
Humboldt University of Berlin

Public International Law

Ms. Ellen Hey
Professor of Public International Law
Erasmus School of Law


David Bachman

Max Planck Encyclopedia of International Law

This premium source include over 1,600 articles by leading scholars on a wide range of topics, broad and narrow; arranged by topic and searchable.


The American Society of International Law (ASIL) provides several research resources, including: