Museum of unintended consequences/Prohibition and Banning in general

From CSWiki

Prohibition [of alcohol in the United States] and the banning of substances and certain activities in general often has unintened consequences. Notable cases are recreational drugs use (including alcohol), gambling and prostitution. Banning often has the effect of driving activity underground rather than preventing it, thus funding organised crime and depriving (or limiting) protection from the law (e.g. if disputing the outcome of a bet) or of medical assistance in the case of banned substance use or prostitution.

More 'developed' policies and laws often allow for some controlled partaking in otherwise banned activities with the intention of lessening the unintended consequences, by allowing better monitoring of the activities and also providing access to legal and health services.