In the United States, the use and possession of cannabis is illegal under federal law for any purpose, by way of the Controlled Substances Act of 1970. Under the CSA, cannabis is classified as a Schedule I substance, determined to have a high potential for abuse and no accepted medical use – thereby prohibiting even medical use of the drug. At the state level, however, policies regarding the medical and recreational use of cannabis vary greatly, and in many states conflict significantly with federal law.