The internationally accepted classification of sources of international law is formulated in Article 38 of the Statute of the International Court of Justice. These sources are:

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