Well, it starts with enforcing law. When you say loud and clear to somebody if you're going to carry a gun illegally, we're going to arrest you. If you're going to sell a gun illegally, you need to be arrested. If you commit a crime with a gun, there needs to be absolute certainty in the law.
Guns cannot be traced to the seller.
( z1 possible :polarity - :ARG1 ( z2 trace :ARG1 ( z3 gun ) :ARG2 ( z4 person :ARG0-of ( z5 sell ) ) ) )