International law is the set of rules and regulations governing the conduct of international relations. They can include rules on hostilities, the treatment of prisoners, the environment, the commons, world trade, and more. States must abide by these rules and regulations in order to avoid violations. However, the interpretation of international law is not a straightforward process.

International law has a long history, and its roots go back to antiquity. Peace treaties were negotiated and signed by Mesopotamian city-states as far back as 2100 BCE. Later, polities throughout the world negotiated and signed various international treaties, from the eastern Mediterranean to East Asia.

International law aims to ensure that a state abides by its commitments to the welfare of its citizens. It protects the interests of its citizens and promotes peace and security. It also promotes trade, justice, and common interests. As countries become increasingly interdependent, international law becomes more important.

Although the UN Charter is the basis of international law, it is not a comprehensive rulebook. Since World War II, countries have signed countless treaties covering everything from the most mundane to the most profound issues. These treaties have created a body of rules and regulations that govern international relations. The interactive below explores ten of these treaties.

Customary international law is another source of international law. According to article 38 of the Statute of the International Court of Justice, customary international law refers to “evidence of a common practice accepted as law.” It also includes subjective convictions about international law known as opinio juris.