In time, of course, the militia idea died out, replaced by a professionalized armed service. Most gun regulation took place at the state and city level. The judiciary mostly stayed out of the way. In 1939, the Supreme Court upheld the nation’s first national gun law, the National Firearms Act, which put onerous limits on sawed-off shotguns and machine guns — precisely because the guns had no “reasonable relation” to “a well-regulated militia.”
But then, in 1977, there was a coup at the National Rifle Association, which was taken over by Second Amendment fundamentalists. Over the course of the next 30 years, they set out to do nothing less than change the meaning of the Second Amendment, so that it’s final phrase — “shall not be infringed” — referred to an individual right to keep and bear arms, rather than a collective right for the common defense.