@Computersaysno
Is there some special hell people get sent to if they're killed by gunfire? Dead is dead.
The only difference the weapon makes is on the side of those defending themselves. Not everyone can wield a knife or a club to the same effect as someone larger, stronger, or more experienced than themselves, but anyone can use a gun. They are equalizers.
What you're proposing is going back to the days when strong people preye...
There is already a law against producing an undetectable firearm. The metal strip they put into the gun, along with the nail firing pin makes the gun detectable and legal.