Article 38 of the Statute of the International Court of Justice enumerates the sources where the rules of international law may be found. The article reads as follows:

“1. The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:

1. International conventions, whether general or particular, establishing rules expressly recognized by the contesting states;
2. International custom, as evidence of a general practice, accepted as law;
3. The general principles of law recognized by civilized nations;
4. Subject to provisions of Article 59, judicial decisions and the teachings of the most highly qualified publcist of the various nations as subsidiary means for the determination of rules of law.

As also understood from the information given, the correct answer is E.