Prohibition is one social response to vice. Prohibition, however, doesn't go far in characterizing a policy regime. Precisely what is prohibited? In the case of drugs, is possession prohibited? Sale? Manufacture? Purchase? Marketing of related paraphernalia? In the case of prostitution, is all prostitution prohibited, or just streetwalking? Is soliciting illegal? Are clients (buyers, johns) engaging in a criminal act? Is it illegal for someone to “live off of the proceeds” of prostitution? Once it is clear precisely what behavior is prohibited – and it might not be all that clear – there is still the issue of how intensely the prohibition is policed, and what sanctions are imposed on those who are found to be in violation. Swimming is prohibited in Lake Michigan off the promontory near where I live, but lots of swimming takes place there during the summertime despite the ban, and sometimes publicly paid lifeguards are on duty in areas where, officially, swimming is banned. In the Netherlands, possession and sale of cannabis is officially illegal, but government licensed “coffee shops” openly sell marijuana and hashish. The term “prohibition” connotes uncompromising rigor, but prohibitions themselves range over the full spectrum from very lax to very strict controls.

Attempts to gauge the effects of a vice prohibition require not only specifying the precise nature of the prohibition and its enforcement but also the relevant alternative policy regime. Furthermore, the impact of a ban in one locale depends on the policies pursued in other jurisdictions.