In the United States, cannabis exists in a legal gray zone—a patchwork of conflicting policies that highlights the enduring tension between federal authority and states’ rights. While federally classified as an illegal drug, cannabis has been legalized in some form by a majority of states over the past three decades, reshaping public opinion, economies, and law enforcement priorities.
Cannabis was not always controversial in the U.S. It was widely legal until the early 20th century, when a wave of state-level prohibitions began between 1916 and 1931. The 1937 Marihuana Tax Act effectively banned it nationwide, a policy later embedded in the 1970 Controlled Substances Act, where it remains a Schedule I drug—deemed to have no medical value and a high potential for abuse.
The modern legalization movement took root in 1996, when California voters passed Proposition 215, legalizing medical cannabis. That vote framed cannabis regulation as a matter of state autonomy, setting the stage for ongoing conflict with federal law.