West's Encyclopedia of American Law | Militia

A group of private citizens who train for military duty in order to be ready to defend their state or country in times of emergency. A militia is distinct from regular military forces, which are units of professional soldiers maintained both in war and peace by the federal government.

In the United States, as of the early 2000s, the NATIONAL GUARD serves as the nation's militia. Made up of volunteers, the National Guard acts under the dual authority of both the federal and state governments. According to the Constitution, Congress can call the National Guard into federal service for three purposes: to enforce federal laws, to suppress insurrections, and to defend against invasions. State governors can call upon the National Guard for emergencies that are prescribed by state law.

The American militia system has its roots in ancient English tradition,...