As Justice Scalia has noted, "It would be strange to find in the midst of a catalog of the rights of individuals a provision securing to the states the right to maintain a designated 'Militia.'" Antonin Scalia, A Matter of Interpretation: Federal Courts and the Law 3, 42-43 (Princeton Univ. Press; Princeton, N.J.; 1997).
Since many seem to endorse firearms registration, there is a Supreme Court decision there which should be noted, Haynes, USSC. 1968. In that case the Court held that criminals could not be required to register firearms as that would violate their rights under the Fifth Amendment. Any such law, anywhere in the United States, applies only to lawful gun owners according to the Constitution as interpreted by the Supreme Court.
Easy to obtain guns ended in the mid 60's, prior to that you could even get them by mail order. Of course, back then there wasn't nearly so much crime.
I wonder if there is any relationship there--guns easy to get and low violent crime rates, versus guns hard to get and high violent crime rates...