Historically, cannabis was legal and used medicinally in the UK well into the 19th and early 20th centuries. Restrictions began escalating in the 1920s, culminating in the 1971 Misuse of Drugs Act that heavily criminalized cannabis. This shift was influenced by social, political, and racial factors as well as international drug control treaties. The recent legal changes for medical cannabis mark a reversal of sorts, but the legacy of prohibition still shapes public policy and perceptions today.