The legal history of cannabis in the United States pertains to the regulation of cannabis (legal term marijuana or marihuana) for medical, recreational, and industrial purposes in the United States. Increased restrictions and labeling of cannabis as a poison began in many states from 1906 onward, and outright prohibitions began in the 1920s. By the mid-1930s cannabis was regulated as a drug in every state, including 35 states that adopted the Uniform State Narcotic Drug Act. The first national regulation was the Marihuana Tax Act of 1937.
Cannabis was officially outlawed for any use (medical included) with the passage of the 1970 Controlled Substances Act (CSA). Multiple efforts to reschedule cannabis under the CSA have failed, and the U.S. Supreme Court ruled in United States v. Oakland Cannabis Buyers’ Cooperative and Gonzales v. Raich that the federal government has a right to regulate and criminalize cannabis, even for medical purposes. Despite this, states and other jurisdictions have continued to implement policies that conflict with federal law, beginning with the passage of California’s Proposition 215 in 1996. By 2016 a majority of states had legalized medical cannabis, and in 2012 the first two states, Colorado and Washington, legalized recreational use.