International law governs relations between states and is an ever-changing area of study and practice. While most international law headlines are about high-profile conflicts, the subject has influenced many areas of national policy, from human rights to global trade and finance. Traditionally, the scope of international law was limited to agreements between sovereign states. However, that has slowly changed, and now international law encompasses a broader range of subjects.

Some of the oldest international law treaties date back to the 18th century. These treaties established institutions for the regulation of state behavior. These bodies include the Permanent Court of Arbitration and the Geneva Convention. Nevertheless, the modern concept of state sovereignty is comparatively recent, having risen in popularity as more governments became states in the 18th and 19th centuries.

One of the first authors to write about international law is Alberico Gentili, who is considered the father of secular international law. In his De jure belli libri tres, Gentili discusses the laws of war and treaties in an expansive manner. It is a collection of three books that outlines the basic principles of international law.

There are many judicial bodies and tribunals established internationally. Some are affiliated with the United Nations, while others are independent of the organization. The UN Charter has many objectives and is intended to foster international law and uphold justice. It also seeks to protect human rights and respect international treaties.