Interesting. Was this law ever repealed?
It was replaced in 1903 by the Dick Act which gave us the National Guard.
The pertinent part is reflected in 10 USC 311 as follows:
10 USC Sec. 311
-EXPCITE-
TITLE 10 - ARMED FORCES
Subtitle A - General Military Law
PART I - ORGANIZATION AND GENERAL MILITARY POWERS
CHAPTER 13 - THE MILITIA
-HEAD-
Sec. 311. Militia: composition and classes
-STATUTE-
(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.
10 USC 312 lists exemptions.
I don't know what minor adjustments may have been made over the years.
I think other sections of the US Code address equipping the National Guard and so forth.
I don't know of anything that addresses equipping the unorganized militia.
You can search the US Code here: US Code
Wikipedia has an article here: Militia