President Richard Nixon declared a "war on drugs" in 1971. The expectation then was that drug trafficking in the United States could be greatly reduced in a short time through federal policing—and yet the war on drugs continues to this day. The cost has been large in terms of lives, money and the well-being of many Americans, especially the poor and less educated. By most accounts, the gains from the war have been modest at best.

The direct monetary cost to American taxpayers of the war on drugs includes spending...