Legalise the damn stuff
When I used to smoke the cursed weed, the biggest danger I put myself in was actually getting hold of it.
I ended up in some pretty scary places with some very unhinged people, not to mention the potential of being arrested and thrown in the slammer.
So, you put drug users through a double whammy when you make it illegal - the risk of obtaining it and the risk of legal action, both of which could end up far more harmful to the individual than the drug itself. (aside from the obvious hard drugs)
Then there's the entire 'teenage rebellion' thing - the thrill of doing something illegal. That, in itself, probably results in more drug usage. A percentage of those teens will become addicts or habitual users.
Finally, there's the bad weed - the super skunk varieties that seem so prevalent now - that's completely out of control. The weed is so strong in a psychoactive way, it puts the user at risk of schizophrenia - extreme mood swings.
If it were legalised, the quality and strength could be properly regulated. We know all weed isn't created equal. Just like booze, different weed results in different buzzes, some bad and some good.
Despite the fact that I now consider weed something which screwed with my progress through life quite badly, I reckon if it was legal when I was young, I may never have bothered in the first place.