The way I understood it prohibition was borne out of the temperance movement which had its beginnings in the early part of the 19th century. That movement culminated into the passage of the Volstead Act and the ratification of the 18th amendment, which prohibited the sale of alcohol. Even though that was the case, the government's ability to control the sale of alcohol was very poor (although it did succeed in reducing the consumption of alcohol). Due to its increasing unpopularity, both the 18th Amendment and the Volstead Act were repealed in 1933. Today the government addresses drug abuse mainly through regulation and international treaties. The Controlled Substance Act is the U.S. federal policy with governs the regulation of the manufacture, trafficking, sale and possession of certain substances. Its implementation is in concurrence with the United Nation's Single Convention on Narcotic Drugs -- and international treaty designed to prohibit the production and supply of certain narcotics. Because the CSA is in compliance with the treaty it is law of the land and suffices as the authority to regulate, prohibit and enforce illegal drugs, their production, sale, and possession.