The legalization of drugs usually come with a program that sets drug addiction as an health problem, and does not make it an ordinary good.

Also, I am not sure if the gun legalization would increase crime by itself. The laws made to allow the use of guns probably do more harm. Here (in France), guns are restricted but allowed in some conditions, and they aren’t much linked to crime. Also, what ever crime is punished far more if the offender had a weapon, which makes most criminals avoid weapons when they are not strictly needed…