Maybe we should study what the Taliban did more closely, when they went at opium for a bit, for lessons learned.
Actually that isn't a bad idea. I doubt that we could replicate their behavior and success, but it would still be interesting to explore:

+ how they reduced the trade
+ what the impact was on the farmers and others
+ how the farmers and others adapted
+ "why" the farmers went back to growing opium after the Taliban were forced out of power

If we could answer these factually (not based on assumptions) then it would probably yield some interesting insights in our never ending pursuit of a better way.