The Second Amendment itself states its entire justification as "a well regulated militia being necessary to the security of a free state." So there is every constitutional basis for regulating the HELL out of arms; they could even be made conditional on militia membership. Banning or confiscating guns would be totally unconstitutional, obviously, but regulating them is perfectly valid. Machine guns, for example, have been illegal without federal registration and permits for about 80 years, and no ones constitutional rights were violated.