International law governs the relations between two or more states, or a state and a private party. It is, generally speaking, split up into two areas: private international law and public international law. Private international law includes topics such as conflict of laws and those situations involving private transactions between private parties. Public international law governs relationships between national governments and inter-governmental organizations.
A few more terms to be familiar with:
Comparative law: study of comparing the laws of two or more countries.
Transnational law: laws that regulation actions/events that extend across national borders.
Supranational law: organization that has powers that its members do not have because they handed over those powers to it. The European Union is an example of a supernational organization.
Article 38 of the International Court of Justice Statute lays ouf the following sources of international law:
"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 detremination of rules of law."
International conventions are covered in the Treaties section of this research guide. International custom and the general principles of law are covered under the Customary International Law section. Judicial decisions are covered under the International case law section. Teachings of the most highly qualified publicists are covered in the Secondary Sources tab.