Treaties have been classified into “general” and “particular”, as is done in Article 38(l)(a) of the Statute of the ICJ.

A treaty, even if of universal or normative nature, will not bind the non-parties unless they (expressly or by their conduct) manifest their intention to be bound by the provisions of the treaty as general rules of international law.

Some jurists have further classified the treaties into lawmaking treaties and treaty contracts. Whereas the law-making treaties are a source of law, the treaty contracts merely purport to lay down special obligations between the parties and are not directly a source of law.

A treaty is an express manifestation of the parties’ intention to be bound by a particular rule, and it can modify or reject the existing customary rules. Hence, treaty law takes priority over international customary law. In those situations where there is a conflict between a treaty rule and a customary rule, the judicial bodies have to give effect to the treaty provision.