The law that governs the relations between nations during times of peace and war.

Today, international law is an expansive concept that encompasses a variety of agreements, norms, and customs governing all human activity. It is used to address a wide range of issues, from trade and commerce to the global environment, public safety, and even international cyberspace.

The development of international law can be traced back to the 15th century, when a series of factors converged to spur an accelerated development of legal concepts and institutions. These included the influx of Greek scholars from the collapsed Byzantine Empire, the introduction of the printing press, and the growth of centralized states that required sophisticated rules of conduct.

In the years that followed, international law developed additional principles and conventions to regulate the conduct of states at times of war. In addition, the Nuremberg Trials after WWII identified individual responsibility as a central principle of international law.

Since that time, a number of developments have occurred that have significantly altered the way in which international law is used. The most significant of these is the growing emphasis on identifying and protecting the rights of individuals, particularly in areas such as criminal law.

The emergence of the International Criminal Court (ICC) in 1998 represents one such important development. It provides jurisdiction to prosecute genocide, crimes against humanity, and war crimes. However, this jurisdiction is limited to 123 countries, and government withdrawal from the ICC is possible.