While there have always been norms and customs around the use of drugs, explicit public policies--regulations, taxes, and prohibitions--designed to control drug abuse are a more recent phenomenon. Those policies sometimes have terrible side-effects: most prominently the development of criminal enterprises dealing in forbidden (or untaxed) drugs and the use of the profits of drug-dealing to finance insurgency and terrorism. Neither a drug-free world nor a world of free drugs seems to be on offer, leaving citizens and officials to face the age-old problem: What are we going to do about drugs?...