Any time you want to force someone to do or not to do something, you are calling for force.  Non-compliance implies violence, so there is no non-violent method.   often time it is followed by a lengthy prosecution and long stays in jail.
 it is lose for everyone from the addicts to the taxpayers, but a boon to certain folks in the court/prison/rehab process.  There are many things that are addicting-sugar, cheese, world of warcraft, etc, but people don't usually commit crimes to have those-and it is likely because they are readily available anytime to those who want them relatively inexpensive.

  Aside from where youths are involved, just let people mess up their own lives.  One way or another, the problem will either take care of itself and for all the world to observe how bad drugs are and hopefully avoid them, or the addicts will hit rock bottom and seek out professional help.