Restatement of Foreign Relations
See also Section 103 (2) of the Restatement of the Law (Third), The Foreign Relations of the United States. The Restatement presents U.S. law as stated by the American Law Institute. B1 and Reserve KF395.A2 F63T3 1986.
The Restatement Third is searchable in WESTLAW REST-FOREL (requires a password). A "link to new citations" appears at the top of the document if there are newer cases for the section that you are reading.
You may also need to research "foreign" law.
If your international law issue or transaction involves nationals or companies from multiple jurisdictions, or if you are researching customary international law, you may need to research the law of other jurisdictions, too. The law of a country other than your own is referred to as "foreign law," "municipal law" or "domestic law."
Statute of the ICJ, art. 38(1), 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.
ICJ Statute: citation and commentary
The Statute of the International Court of Justice appears at the end of the Charter of the United Nations. Citation: Statute of the International Court of Justice, art. 38, para. 1.