Arizona Sheriff Joe Arpaio Lets Vigilante Patrols Loose To ‘Protect’ Schools

[jody]

23. See 10 USC § 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.

http://www.law.cornell.edu/uscode/search/display.html?terms=militia&url=/uscode/html/uscode10/usc_sec_10_00000311----000-.html

Depending on your state's own definition of militia, you could be part of its unorganized militia.

One state includes both male and female 17 to 64.