The field of international law has evolved over the years. Its origins date back to 1860, when Theodore Woolsey wrote a book called Introduction to the Study of International Law. Woolsey stated that the concept of international law was the establishment of the idea that nations are self-governing, without external human power imposing a law on them. In his book, he also emphasized the importance of national moral responsibility. The principles he outlined have remained relevant today and have led to the development of public international law.

International law can regulate everything from the conduct of hostilities to the treatment of prisoners of war. It can regulate global commons and communications, and can guide world trade. Generally, most nations observe these principles and obligations. There are many differences in the implementation of international law, but there are some basic principles that are common to all nations.

A state may be a country or a territorial entity, or it can be an entity that is a state. The status of a sovereign state is a privilege that comes with membership in the international society of states. Certain factual criteria are necessary for a territorial entity to gain the status of a state. Often, these criteria are not easy to determine. In some cases, a state has been recognised even though it did not fulfill all the criteria for statehood.

International law is governed by specific treaties that have been signed by countries. Some treaties prohibit the use of certain weapons and other actions. These include cluster munitions and mines. There are also international treaties that prohibit the destruction of cultural property. Many of these treaties were drafted by the International Committee of the Red Cross (ICRC). The ICRC is a private organization, which is based in Geneva.