Glenn Reynolds on the Second Amendment and the options the Supreme Court Faces
It can find that the Second Amendment doesn't grant individual rights, but only protects the right of states to arm their militias (or "state armies," as some gun-control advocates put it). This would make the DC case go away, but at some cost: If states have a constitutional right, as against the federal government, to arm their militias as they see fit, then states that don't like federal gun-control laws could just enroll every law-abiding citizen in the state militia and authorize those citizens to possess machine guns, tanks and other military gear.
This is the first time that I have seen this point. Putting the merits of this approach aside (even DC doesn't appear to really have its heart in this approach), I really wonder if gun control advocates know what they might be getting into if they get their wish regarding the DC gun ban.