The first step is to cut the inflow, then rationalize the system
There are no good fast solutions.
The big problem is that the laws are just plain stupid, and not just the drug laws.
I remember when I was in Georgia, the penalty for busting into a Coke Machine and stealing the quarters was longer than for robbing the 7-11.
Our whole system is screwed up and it will take decades to make the needed changes.
The first step I'd suggest is to start by abolishing all laws below the State level.
Anyone so limited that they can only spell a word one way is severely handicapped!