In a growing number of states, medical marijuana occupies a dual legal status. The federal Controlled Substances Act (CSA) classifies marijuana as a Schedule I drug, signifying that it has both a high potential for abuse and no acceptable medical use. Patients and physicians are thus subject to the same federal criminal penalties as any other individuals who produce, distribute, or possess marijuana. By mid-2009, however, fourteen states had decided to permit medical marijuana under certain circumstances. Through voter initiatives or legislation, these states have exempted patients and physicians from prosecution for violating state laws governing the use, possession, or cultivation of marijuana. The disparate legal regimes have generated much litigation, including two cases that reached the U.S. Supreme Court. Both cases rejected challenges to federal enforcement of the CSA in California, the state with the most liberal provisions on medical marijuana. Under the Court decisions, federal authorities could continue to take action against patients, physicians, and others who were protected under state medical marijuana laws.