The Controlled Substances Act (CSA) is the statute establishing federal U.S. drug policy under which the manufacture, importation, possession, use and distribution of certain substances is regulated. It was passed by the 91st United States Congress as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970 and signed into law by President Richard Nixon.[1] The Act also served as the national implementing legislation for the Single Convention on Narcotic Drugs.

The legislation created five Schedules (classifications), with varying qualifications for a substance to be included in each. Two federal agencies, the Drug Enforcement Administration and the Food and Drug Administration, determine which substances are added to or removed from the various schedules, although the statute passed by Congress created the initial listing. Congress has sometimes scheduled other substances through legislation such as the Hillory J. Farias and Samantha Reid Date-Rape Prevention Act of 2000, which placed gamma hydroxybutyrate in Schedule I. Classification decisions are required to be made on criteria including potential for abuse (an undefined term),[2][3] currently accepted medical use in treatment in the United States, and international treaties.