All you have shown there is that law breakers will break the law. When they are caught; they pay the consequences. Passing drug laws does not ban drugs from existence; they punish the people who make, sell and use them.
Banning guns will not eliminate them from existence, either, and that's the discriminating factor, and why the two issues are not the same argument. There are legislators who want to ban guns and they think it's the solution to the problem and that it is possible. No legislator would suggest that it's possible to ban drugs.