California?s medical marijuana policy has been the subject of much debate and confrontation between federal, state, and local government. The very existence of state sanctioned medical marijuana defies the Controlled Substances Act of 1976 which classifies the drug as Schedule I ? a drug without any accepted medical benefits and a high potential for abuse. The transition in California from an absolute prohibition on marijuana to a state established system of providing marijuana to for a variety of illnesses represents a liberalization of drug policy. The liberalization of drug policy in California has been coincident with the nationwide execution of the War on Drugs. While much attention has been paid to whether the state of California has the right to contradict federal law, relatively little attention has been given to the question of whether such a law has an impact on the criminality of the substance. This report investigates the impact of the liberalization of drug policy on the manner in which the criminal prohibition of marijuana is pursued and enforced. Of central importance are demographic characteristics of arrestees and the degree to which arrests and arrest rates have been impacted by medical marijuana law. The report also seeks to quantify the costs and benefits of maintaining criminal prohibition in its current form.