I keep and bear arms...all of which have serial numbers. In what sense, then, does requiring serial numbers infringe on “the right of the people to keep and bear Arms”?
And Congress does have the right to regulate commerce between states. Some states have considered (passed?) laws affecting handguns made and sold in one state...although the ease with which they could be sold out of state might still put it under Congress’s Constitutional authority.
It’s just another arm of the unconstitutional Wickard wickedness. If you have and keep the gun in your state, its constitutional participation in interstate commerce has ended. A state could constitutionally have something to say about the gun so long as it does not prohibit you from keeping one; but the US government can only get involved with that through unconstitutional action.