International law refers to a body of rules that governs relations between States. These rules, unlike national laws, are not set forth in legislation approved by a parliament, but rather are considered to be binding upon States because they have consented to be bound by them. As a result, international law is derived from many sources, including treaties, custom and state practice and judgments of international tribunals. In addition, there is a significant body of non-legal materials which informs and explains international law, such as books, articles and academic commentaries.

Traditionally, only States were deemed to be subjects of international law (entities capable of possessing rights and obligations under international law), but this doctrine has been gradually broadened to include non-state actors such as individuals and non-governmental international organizations. More recently, it has been extended to cover movements for the liberation of non-self-governing peoples, and even to corporate entities such as multinational corporations and multi-national businesses.

Although international disputes occasionally lead to armed conflict, the overwhelming majority of international law disputes are settled peacefully. Most of the time, this is done through diplomacy, or submission by the disputing states to an international tribunal or court for resolution. In very exceptional circumstances, the UN Security Council may authorize the use of force to enforce international law, but even this is subject to veto by any of the permanent members of the council. The International Court of Justice is the principal judicial organ of the United Nations and has been established by the Charter of the United Nations as the highest judicial authority in the world.