International Criminal Law

The bulk of criminal law is established and enforced under the national law of individual states, but an increasingly important body of international criminal law has also emerged. It began with a few international procedures developed by states to coordinate the enforcement of their national criminal law and has grown as international law itself has come to proscribe certain acts as crimes.

Since the end of the Thirty Year's War in 1648, the international system has been based on state sovereignty, including each state's jurisdiction over its own territory and citizens. A basic system of international law, defining the rights and obligations of states, was needed to recognize and validate this sovereignty, but this decentralized system has no legislature. Instead, international law must arise from one of three primary sources: treaties, customary international law, or general principles of law. Treaties make binding law for those states that agree to accept them. Rules of customary international law develop when the actions of states, their general and consistent practices, demonstrate their implied consent to those rules. General principles of law, especially when common to the laws of many nations, can also be applied at the international level. Judicial decisions and scholarly writings are recognized as secondary sources of international law, and are especially useful as indicators of changes in customary international law. International crimes, and the other substantive aspects of international criminal law, emerge from these same sources.

The traditional focus of international law has been upon the rights and obligations of states, but international criminal law regulates and punishes the conduct of individuals. Many of the crimes now defined by international law involve violations of the human rights of individuals. These too are now recognized under international law.

International criminal law, as the term is used today, includes those aspects of substantive international law that deal with defining and punishing international crimes, as well as the various mechanisms and procedures used by states to facilitate international cooperation in the investigation and enforcement of national criminal law.