The National Guard you are referring to is not a Militia, the Militia, or any kind of Militia, that you are referring to. Both by law and custom. The National Guard is a reserve component of the national army.
TITLE 10, UNITED STATES CODE, Subtitle A, PART I, CHAPTER 13, Sec. 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
311-a and 311-b(1) both name the National Guard as the Militia
Are you rather, thinking of the U.S. Army Reserve? They are a Federal reserve force; the ARNG are not Federal troops, but under the command of the Governors of the state/territory in which they are stationed.