Trust me.
The prisons, contrary to what we're told, are not filled with drug offenders. Those that are in there are overwhelmingly in for dealing and not for getting busted the first time.
The other fundamental mistake many make is assuming the if we decriminalize or legalize, these folks will stop committing crimes. When one avenue of crime is closed to criminals, they seek out another. You will not reduce crime through these policies.
Fred's mention of the military is actually something I've said for a long time about kids who have demonstrated criminal histories. At a certain point, to save them and to spare society, they need to have an ultimatum presented to them: the military or some sort of supervised work program on the order of Huber Law. If they don't choose, we assign them to one. These are the kids who day-after-day assault, harass and steal from other students and staff. At some point as a society, we have to take off the blinders and recognize that we are enabling the predators who terrorize us even more as adults, and waiting until they're adults isn't good enough. I'm tired of 80% of the other kids being held hostage to the 20% there to cause problems and practice their criminal behavior. We show more compassion and devote more resources and time to the 20% than the 80%. It's what I call "misplaced compassion."