There was an anti-gun advocate on NPR who was making the case that the ruling will actually make it easier for authorities to regulate firearms, because the NRA will no longer be able to make the "slippery slope" argument (i.e. if I let you take my machine gun, the next thing you'll want is my fouling piece). If it's already been determined that they can't take the fellow's shotgun, it weakens the argument to let the individual keep the machine gun.