The 1961 UN Single Convention on Narcotic Drugs establishes the following rule in Article 49: “The use of cannabis for other than medical and scientific purposes must be discontinued as soon as possible but in any case within twenty-five years…”
“In 1961, the United Nations adopted the Single Convention on Narcotic Drugs, the terms of which state that each participating country could ‘adopt such measures as may be necessary to prevent misuse of, and illicit traffic in, the leaves of the Cannabis plant.’ Congress approved participation in the convention in 1967 and three years later passed the Comprehensive Drug Abuse Prevention and Control Act, which provides the basis for current federal prohibitions regarding marijuana use.”