The answer to that question in a society that allows (mostly) autonomy of choice is that we let them die on the street.
I'm not convinced that involuntary incarceration will actually fix the problem. I believe it will just take it off of the streets and out of the public consciousness.
>I believe it will just take it off of the streets and out of the public consciousness.
If antisocial people do not exist in the public consciousness, then that means the problem is fixed. Even you never have to worry about locking your front door, then the problem of burglars has been fixed even if technically would be burglars may exist in prison.
Not a great solution, honestly. Long term drug abuse is almost never a victimless habit. I'm tempted to say never.
I have a very good friend who was an addict, and I tried to help him turn his life around in many ways, but I couldn’t figure out a way. Professionals told me “he has to hit rock bottom.”
Anyhow he wound up getting arrested and spent a couple of weeks in jail where he got clean and decided to turn his life around. He went on to get a couple of masters degrees, get married, have two kids, and has a good job. He credits his time in jail for saving his life.