An editorial in today's New York Times, Repeal Prohibition, Again makes the case for legalizing marijuana in the United States. Over the next days, this editorial opinion will be followed up with a series of articles exploring the topic further. The first article in this series explores the role of states: Let States Decide on Marijuana. It is encouraging to see a major newspaper endorsing legalization. However, the editorial concludes with the observation that "We recognize that this Congress is as unlikely to take acton on marijuana as it has been on other big issues. But it is long past time to repeal this version of Prohibition."

There are strong parallels between marijuana prohibition today and alcohol prohibition in the United States (1920-1933) and Canada. It appears that many of the lessons have been forgotten. After its introduction in the United States through the 18th constitutional amendment, the policy quickly failed as the thurst for alcohol could not be legislated away. Instead, enforcement of prohibition was difficult from the beginning, in particular in urban areas where the policy was routinely ignored. Alcohol remained available plentifully through illegal channels—in particular smuggling across the border from Canada where alcohol was already legal again, and home brewing and distilling ("bootlegging"). Of course, quality suffered, and illicit "moonshine" was often contaminated and dangerous. Alcohol prohibition was the fertile ground on which criminal gangs arose—gangs like those of Al Capone in Chicago. Alcohol prohibition was corrosive to society, and caused more harm than it reduced.

Eventually, alcohol prohibition was repealed in 1933 in two steps. First, the Beer Revenue Act legalized beer. Second, the 21st constitutional amendment was passed, leaving prohibition to state governments. While alcohol became legal in most states, some states remained "dry" for long periods afterwards. Alcohol remained illegal in Mississippi until 1966. As states further delegated decisions about alcohol to municipalities, several counties remain "dry" to this day.

The lessons from the "prohibition experiment" were forgotten too quickly. It is impossible to sustain a public policy that suppresses goods that are in robust demand, in particular when the public is not convinced that consumption of these goods is deleterious to one's health. It simply drives consumption into illegality, enriches criminal gangs, and takes control away from governments. The only sensible long-term policy aims at reducing demand through education, treating it as a health issue. It took decades to wean people off tobacco, but that happened through convincing people one person at a time.