The 18th amendment, section one, states,
"After one year from the ratification of this article the manufacture, sale, or transportation of intoxicating liquors within, the importation thereof into, or the exportation thereof from the United States and all territory subject to the jurisdiction thereof for beverage purposes is hereby prohibited."
This doesn't necessarily prohibit people from drinking, just from making/buying alcohol. Does that mean people could have just bought tons of liquor before the law took effect and stocked up, or did the states regulate this individually? Are there any examples of people stockpiling? Thanks!
Yes, very much so. Being drunk wasn't a federal crime. One could drink from your personal supply, assuming it was purchased before 1920, or it was made within the home. Stockpiling occurred on a fairly massive scale beforehand. If a person had the means and will, they stocked up before January 17th, 1920. Some stores had massive sales in the days leading up. Whole warehouses were purchased by some of the larger richer families.
For the most part, people didn't need to worry about being busted for drinking in private houses. Private parties such as weddings would generally be wet events during prohibition without agents crawling around. Thousands of criminal cases were dropped because it couldn't be proven that the alcohol found during a raid or arrest wasn't purchased before prohibition.
People could even make wine or cider in their own house, up to 200 gallons, without trouble. There were several companies selling grape concentrate in a brick-like form. If one dissolved these bricks in water, it would end up becoming wine in a few months. In the four years between 1925 to 1929, an estimated 678 million gallons of home-fermented wine was drunk. In addition, every family was allowed to purchase ten gallons of wine each year for sacramental use.
The main issue with having a stockpile was if one wanted to move to another location. It was, of course, illegal to transport alcohol even if it was for personal use. However, it was not a huge issue if caught. A fine was issued and the liquor would be returned after payment unless one had a very strict judge. When Wilson left the White House in 1921, he had to get a special exemption from Congress to move his wine. Warren Harding had his own supply moved into the White House with getting an exemption. It was probably the first law he broke as president.
Sources
Lerner, Michael A. (2007). Dry Manhattan: Prohibition in New York City. : Harvard University Press.
McGirr, Lisa. (2015). The War on Alcohol: Prohibition and the Rise of the American State. W. W. Norton.
Garrett Peck (2011). Prohibition in Washington, D.C.: How Dry We Weren't. The History Press.