"[T]he enshrinement of constitutional rights
necessarily takes certain policy choices off the
table.... Undoubtedly some think that the
Second Amendment is outmoded in a society
where our standing army is the pride of our
Nation, where well-trained police forces
provide personal security, and where gun
violence is a serious problem. That is perhaps
debatable, but what is not debatable is that it
is not the role of this Court to pronounce the
Second Amendment extinct."