The minute you use the drugs, and you do something that interferes with the life, liberty, and the pursuit of happiness of the guy next door, you're a criminal, and you ought to be punished for that especially if you're in a position where your actions could affect large numbers of people. Being a doctor, a legislator, a judge, an airline pilot, where somebody's life depends on you.
The advent of interconnectedness and of weapons of mass destruction means that, increasingly, I share a destiny with my enemy.