International law is a set of rules and regulations that govern relationships between states, non-state groups, and other international actors. These rules and regulations vary from country to country. However, they have become more important as more countries come to realize the impact that a single nation can have on the global environment.

During the mid-19th century, the primary focus of international law was on relations between sovereign states during wartime. This led to the creation of various treaties that established bodies to regulate the conduct of states. The Hague Convention, signed in 1864, is often considered the foundational text of international law.

Several other treaties were negotiated by polities around the world, including the Geneva Convention. This convention gave protection to civilians during wartime.

In the 21st century, the scope of international law has expanded to include a wide range of entities. Including corporations, non-state organizations, and paramilitary groups. It also covers trade and regulatory issues.

Aside from the treaties and conventions, there is also customary law. These rules are derived from national and regional laws and are similar to those found in international law.

One of the earliest international lawyers was John Stuart Mill. He advocated for the application of international law to all peoples.

Another important development in the history of international law was the introduction of the printing press. This increased the availability of scientific knowledge and spurred the growth of humanism.

Other notable developments included the proliferation of centralized states such as Spain and France. By bringing more commerce and wealth to these nations, these governments were able to create a standardized, more advanced rule set.