Today, as defined by the Militia Act of 1903, the term "militia" is primarily used to describe two groups within the United States:
Organized militia – consisting of State militia forces; notably, the National Guard and Naval Militia.[8] (Note: the National Guard is not to be confused with the National Guard of the United States.)
Unorganized militia – composing the Reserve Militia: every able-bodied man of at least 17 and under 45 years of age, not a member of the National Guard or Naval Militia.[9]
There is a third militia that is widely unknown to most. This militia is called a state defense force.They are authorized by state and federal laws.