Article 38 of the Statute of the International Court of Justice lists 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, 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.
2. This provision shall not prejudice the power of the Court to decide a case ex aequo et bono, if the parties agree thereto.
This guide briefly examines each of these sources. For additional information, please consult separate research guides on U.S. Treaties and International Agreements, World Treaties, and United Nations Documents. The international law resources listed in these guides are available on the Internet or in the Heafey Law Library collection. Be sure to note the specific locations listed for individual items. If you need some help locating materials, please stop by Research Services.
Another discussion of the sources of international law appears in The Restatement of the Law (Third) The Foreign Relations Law of the United States, Sections 102, Sources of International Law, and 103, Evidence of International Law.
EISIL (Electronic Information System for International Law): www.eisil.org
Identification of and citations for major conventions in various international law topics; links to online texts
ASIL Electronic Resource Guide (ERG): http://www.asil.org/resources/electronic-resource-guide-erg
American Society of International Law guide for selected public and private international law topics
Many additional research guides are available on the Internet. Use general terms such as international legal research or more specific terms -- treaty research, international courts and tribunals -- in internet search engines.