The movement to legalize marijuana has enjoyed an unbroken string of victories on the state level over the last decade. But as Congress considers nationwide legalization, proponents of legal cannabis are making the same empty promises they made to the residents of every state that took their advice.

They spoke of marijuana as a harmless drug that gave a cheap high and nothing more — not at all like the deadlier hard drugs such as meth and opioids, with their unhealthy and even lethal consequences. They also downplayed the idea that widespread drug use would bring about societal maladies.