International Law, according to the Restatement of the Law (Third), the Foreign Relations of the United States, "consists of rules and principles of general application dealing with the conduct of states and of international organizations and with their relations inter se, as well as with some of their relations with persons, whether natural or juridical."
More basically, International law refers to the law governing interactions between nations. International law can be divided into two distinct categories:
Public International law focuses on relationships between nations and citizens of different nations as governed by various inter-governmental organizations, such as the United Nations and NATO, and other sources of law such as treaties and custom. For example, a dispute over a waterway between two nations would be governed by Public International law.
Private International law is synonymous with the concept of "conflict of laws"; that is, it refers to legal disputes, typically involving private citizens, in which jurisdictional issues are the primary area of inquiry. For example, a contract dispute between citizens of two different countries would likely be governed by Private International law.
This guide focuses on Public International Law, but because the two areas overlap, some resources may also be helpful in researching Private International Law.
Article 38 of the Statute of the International Court of Justice establishes five distinct sources of international law:
Note that only the first three categories, international conventions (i.e. treaties), international custom, and the general principles of law recognized by civilized nations, are considered primary sources of law. Case law and scholarly works are considered "subsidiary" sources of law and thus are not necessarily binding.
When faced with a research problem in Public International law, you will need to consult some or all of these sources, depending on the issue at hand.
Approaching a research problem in Public International Law shares many similarities to approaching an American legal research problem though the materials used may differ.