In the absence of any evidence tending to show that possession
or use of a 'shotgun having a barrel of less than eighteen inches
in length' at this time has some reasonable relationship to the
preservation or efficiency of a well regulated militia, we cannot
say that the Second Amendment guarantees the right to keep and bear
such an instrument. [...] The Militia comprised all males
physically capable of acting in concert for the common defense.
-- Majority Supreme Court opinion in "U.S. vs. Miller" (1939)