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.
It is illegal to buy a firearm but not to sell one.
( z1 legal :polarity - :ARG1 ( z2 contrast :ARG1 ( z3 buy :ARG1 ( z4 firearm ) ) :ARG2 ( z5 sell :polarity - :ARG1 z4 ) ) )