But we do not criminalize smoking, even for the limited purpose of forcing smokers into treatment programs. Instead, we reserve the criminal law for the small category of bad acts that are so bad that society cannot tolerate them on an ongoing basis. Any discussion of what to do with Robert Downey, Jr. must proceed from there. Drugs are illegal because buying, selling, and using them are harmful. Drugs hurt those who use them, of course, but that's just the beginning.
Every drug deal robs a community of a street corner.
Even if drugs were legal, any public gathering of cocaine users would still be an unpredictable, degraded, dangerous place. When the justice system treats a drug user, it is trying to do two things at once. It is trying to help the defendant, obviously, but it is also trying to help the rest of us. If the drug user stops using, then everyone wins. But if he doesn't stop, then the system has to choose.