The Supreme Court has already ruled on this issue. It ruled that the type of weapon that is available to the public could be regulated by using licenses to determine if the person buying that gun would be a public menace. That is why it takes a special license to own a fully auto .45 Thompson. That rule should extended to all the semi-auto assault rifles. Furthermore, the magazines should be limited to no more than 10 rounds. That would at least slow down the crazy.
Semi-automatic fire is just as deadly as automatic fire. Changing a magazine takes about 3 seconds so having a 10 round magazine is no handicap for the shooter. In three years of Infantry combat I was involved in 4 big battles and many firefights. I never selected automatic fire one time. Each rifle squad has 2 designated automatic rifleman and the rest of the squad can only select semi-automatic fire. Even if there were restrictions on magazine capacity and automatic fire, the crazies would still beat the system.