The
Bureau of Prohibition (or
Prohibition Unit) was the
federal law enforcement agency formed to enforce the
National Prohibition Act of 1919, commonly known as the Volstead Act, which backed up the
18th Amendment to the
United States Constitution regarding the
prohibition of the manufacture, sale, and transportation of
alcoholic beverages. When it was first established in 1920, it was a unit of the
Bureau of Internal Revenue. On April 1, 1927, it became an independent entity within the
Department of the Treasury, changing its name from the
Prohibition Unit to the
Bureau of Prohibition. In 1930, it became part of the
Department of Justice. By 1933, with the Repeal of Prohibition imminent, it was briefly absorbed into the
FBI, or "Division of Investigation" as it was then called, and became the Bureau's "Alcohol Beverage Unit," though, for practical purposes it continued to operate as a separate agency. Very shortly after that, once Repeal became a reality, and the only federal laws regarding alcoholic beverages being their taxation, it was switched back to Treasury, where it was renamed the
Alcohol Tax Unit.