From CalGunLaws.com:

The sources of criminal intent are reasonably well known, having been over-studied by working criminologists. Nowhere in the literature are guns shown to instigate crime. Criminals and murderers are predisposed to wanting to rob, rape or murder. Once this course is set, only then does the option to misuse a firearm enter their minds. Criminals choose their trade first, then acquire the tool to practice it. Again, the trigger does not pull the finger, and no law will prevent criminals from accessing a firearm on the black market or making one themselves. Prohibition didn’t work for alcohol, doesn’t work for drugs; it wouldn’t work for guns either.