International law is a set of rules and principles that govern the interactions between states, international organizations and individuals. It regulates issues such as international trade, creation and dissolution of states, use of force (when a state may initiate force against another), armed conflict (“humanitarian law”), human rights, refugees, crimes, the environment, labor, the sea, air space, postal services, and more.

Treaties and conventions between states are the most common sources of international law. Other sources include customary law and general principles which are regarded as common to systems of national law.

A number of ad hoc and UN-assisted tribunals have varying degrees of relation to the United Nations, including the International Court of Justice and a variety of special courts and international tribunals (such as the Special Tribunal for Rwanda and Sierra Leone, the Extraordinary Chambers in the Courts of Cambodia and the Special Tribunal for Lebanon).

The development of international law has been driven by the changing political and economic interests of countries around the world. These differences in political and economic structures and cultures, combined with a new understanding of basic notions of governance and political relations, gave rise to the globalization of international law in the twentieth century.

Traditionally, international law focused on questions of rights between nations, but in recent years it has expanded to include private actors and non-state entities such as corporations and organizations. It is a complex area that can involve many different languages and requires frequent travel.