The textbook competitive model of drug markets predicts that greater law enforcement leads to higher black market prices, but also to the unintended consequences of greater revenue and violence. These predictions are not in accord with the paradoxical outcomes evinced by recent history in some...

Laws that prohibit, regulate, or tax cigarettes can generate illicit markets for tobacco products. Illicit markets both reduce the efficacy of policies intended to improve public health and create harms of their own. Enforcement can reduce evasion but creates additional harms, including...