[asdff]

>you have a substance that you know, for a fact, a certain proportion of the population will abuse, to the detriment of both themselves and society at large

The problem is you can extend this to all sorts of things that people abuse. Sugar, video games, alcohol, caffeine, etc. The solution is not to put people in jail and ruin their lives, its to educate them on the risks and to provide solutions to get help when needed.