§311. Militia: composition and classes
(a) The militia of the United States consists of all able-bodied males at least 17 years of age and, except as provided in section 313 of title 32, under 45 years of age who are, or who have made a declaration of intention to become, citizens of the United States and of female citizens of the United States who are members of the National Guard.
(b) The classes of the militia are
(1) the organized militia, which consists of the National Guard and the Naval Militia; and
(2) the unorganized militia, which consists of the members of the militia who are not members of the National Guard or the Naval Militia.
From WIKIPEDIA:
Today, the term militia is used to describe a number of groups within the United States. Primarily, these are:
The organized militia defined by the Militia Act of 1903, which repealed section two hundred thirty-two and sections 1625 - 1660 of title sixteen of the Revised Statutes, consists of State militia forces, notably the National Guard and the Naval Militia.[2] The National Guard, however, is not to be confused with the National Guard of the United States, which is a federally recognized reserve military force of the U.S. Army and the U.S. Air Force, although the two are linked.
The reserve militia[3] are part of the unorganized militia defined by the Militia Act of 1903 as consisting of every able-bodied man of at least 17 and under 45 years of age who is not a member of the National Guard or Naval Militia.
Former members of the armed forces are also considered part of the "unorganized militia" per Sec 313 Title 32 of the US Code.[2]
It's still part of federal law.