On October 28, 1919, Congress passed the “National Prohibition Act”. The Act (also commonly known as the “Volstead Act”) spelled out how prohibition was to be enforced. The law remained in effect until the 21st Amendment was passed.
You can read the Act in the Congressional Record at https://goo.gl/piDWoj. Enjoy this short, entertaining, fictional clip that attempts to reenact what life was like once the Act went into effect– http://goo.gl/rKghLa.