Terrs, BTW, would have little problem obtaining weapons regardless of what laws were in place. Italy, for example, has stringent gun control, which did nothing to stop two airports there from being shot up and an American 13-year-old killed, back in the '80s. It DID, however, ensure that the targets would be helpless to defend themselves.
Oh, and the jackals of 9-11 used no guns at all, and slew 3,000+ Americans.