Originally Posted by BFT3K

Shy of a ban on assault rifles, which may have reduced the number of shots fired in the theater, it is unlikely any laws would have prevented this.

He bought all of his guns and ammo legally, he didn't have a criminal record, he wasn't considered mentally unfit, etc.

You can't protect society against every lunatic. People are unstable, and no one is a crazy murderer, until they are a crazy murderer.

What if instead of using a gun he waited until a crowd of people assembled outside the theater and mowed them all down with a vehicle instead... do you ban vehicles?

Crazy people are crazy. You can't create laws that prevent or protect us from random insanity.