Whether a country is governed by national law or international law is a matter of debate. There are many people who believe that the nation-state is the primary unit of international affairs. Others argue that a nation’s legal system is a part of international law and that international law applies to the nation.
The concept of nation-state developed rapidly after the Peace of Westphalia in 1648. It was later established as a legal entity with its own sovereignty and independence. This was a major event in international law.
The concept of natural law also remained influential during the 18th century. It challenged Hobbesian notions of war and argued for the principle of jus gentium, which would govern the relations of polities.
In the 19th century, a school of international law emerged, inspired by the positivist tradition. It combined elements of natural law with the secular world of the time.
In the 20th century, the concept of natural rights gained importance. The United Nations Security Council, the Court of Arbitration for Sport, and the International Criminal Court all claim universal jurisdiction when a national system fails.
The United States typically abides by international law. There are some exceptions to this rule, including the Civil War.
In the United States, a federal law is a bill that has passed both houses of Congress. These laws are published in the United States Code. They may be signed by the president, or they may be approved by the president without his signature.