The foundation of military law is the Constitution of the United States. The Constitution provides that Congress has responsibilities to make rules to regulate the military; it also establishes the President as Commander in Chief of the armed forces. Congress has exclusive control of the law governing the nation's military. All persons serving in the Armed Forces of the United States are subject to military law at all times. However, members of the Army National Guard or the Air National Guard are not subject to the Uniform Code of Military Justice unless performing Federal service.
Military law consists of the Uniform Code of Military Justice (UCMJ) and other statutory provisions for the government of persons in the Armed Forces to which may be added the unwritten common law of the usage and custom of military service as well as regulations and authorized by the President as Commander in Chief of the Armed Forces. The UCMJ is essentially a complete set of criminal laws. It includes many crimes punished under civilian law (e.g., murder, rape, drug use, larceny, drunk driving, etc.), but it goes beyond that to punish other conduct which affects good order and discipline in the military. Military law is enforced by civil courts in time of peace as well as in time of war.
