I just saw this image on the Facebook:
Ironically, this is an excellent argument against any kind of victimless prohibitions. ("Ironically", because obviously this is not what the author of the meme meant.) Yes, banning guns only gives them into the hands of criminals. The same with banning drugs or prostitution. As a result of the government banning stuff, there is a whole necessarily shady element of society out there doing things that we have banned... Banning alcohol creates Al Capone. Banning narcotics creates Columbian drug lords. Banning prostitution creates violent pimps.
So, what's the point of the laws? Why do we have them at all?
We have laws for peaceful resolution of conflict. For instance, if I play music loudly late at night, this creates a conflict between me and my neighbors. A law will create a clear boundary that will demonstrate who is violating whose rights. (This law can come from a legislative monopoly like we have today or from independent competing experts selected for by the market.)
Note that in here I am talking about civil laws. Laws created by the people for the people. I.e., laws that everyone agrees on for everyone's prosperity. Not "take of your shoes when entering my house" kind of laws. For distinction between the two, see this post:
Modern States and Dina D'Malchusa Dina