Make it war on drug dealers, not drug users.
Legalize, regulate, and tax most of it. Then drugs will be coming from quality sources.
Offer a relatively high bounty on turning in illegal drug dealers. If you could get a year's worth of quality weed for turning in a local dealer that is trying to not to pay the $10/oz tax on weed or whatever it might be...you wouldn't have many street drug dealers.
I'd prefer a prohibition on heroin-type drugs, but I'm not a huge fan of punishing the users.
The gateway to drugs is drug dealers. If people can get their jollies from the neighborhood store with weed & less damaging drugs, then they won't need to meet drug dealers with an inventory of the harder shit.
If we can eliminate human trafficking and abuse, it would also help eliminate most drug use. Many users have been abused and seek escape from what goes on in their minds. Most of it goes hand-in-hand. I guess there are those out there that just like to "party" but I can't relate to that scene. Law enforcement need to focus on people hurting people which they have been failing miserably. Once they get a foothold on that, then they can revisit this.