How would any of it have stopped Adam Lanza or James Holmes?
It wouldn't, nor will it stop a single gang banger from arming himself and shooting up a block full of kids. It's the fascist's attempt to deprive the citizen of his rights by making it a nuisance to legally own a firearm.
Adam Lanza succeeded doing in Newtown what 0bama/Holder tried to do with F&F, plain and simple.