It doesn't matter what the laws are regarding gun restrictions or bans - it is not going to stop needless killings like the Colorado murders. Laws are for honest people. It is our constitutional right to bear arms and 99% of us are responsible gun owners but there will always be crazies out there that if their intent is to kill like Holmes did, will find a way. He could have easily thrown a bomb instead of a smoke screen. He had the knowledge, the materials, etc.
Personally I think there would be major opposition if the government thinks they could take away our 2nd ammendment rights. I don't know of any legal gun owner that will willingly surrender their arms. We would all be sitting ducks for our already corrupt government.