a. “Well-Regulated Militia.” In United States v.
Miller, 307 U. S. 174, 179 (1939), we explained that “the
> Militia comprised all males physically capable of acting in
> concert for the common defense.” That definition comports
> with founding-era sources. See, e.g., Webster (“The militia
> of a country are the able bodied men organized into companies,
> regiments and brigades . . . and required by law to
> attend military exercises on certain days only, but at other
> times left to pursue their usual occupations”); The Federalist
No. 46, pp. 329, 334 (B. Wright ed. 1961) (J. Madison)
(“near half a million of citizens with arms in their hands”);
Letter to Destutt de Tracy (Jan. 26, 1811), in The Portable
Thomas Jefferson 520, 524 (M. Peterson ed. 1975) (“[T]he
militia of the State, that is to say, of every man in it able
to bear arms”).