Federal marijuana enforcement influences the extent of marijuana consumption only negligibly, while worsening the effects on persistent users and increasing the wealth and power of criminal organizations as well as their use of violence and corruption. Legalization as an alternative requires the construction of a regulatory scheme. Although legalization would largely eliminate black-market costs in illicit revenues, enforcement expenditure, and violence and corruption, it would increase consumption. This could in turn create other law enforcement problems from behaviors stemming from increased consumption. Decriminalization -- treating marijuana consumption and possession for private use as either legal or only mildly punishable while leaving its distribution as a criminal offense -- saves enforcement costs and avoids criminalizing a widespread activity, but it may lead to increased consumption in the long run. Reduced enforcement seems less risky as regards the creation of serious undesirable consequences. 19 notes.