De-criminalise ALL drugs, make them available thru' Doctors and Pharmacy's at prices that compare with standard medicines.
Make every user who buys from Doctor or Chemist fill in an "addict registration"
Make every "wanna have a try" person who goes to purchase drugs from legal sources have a certificate of validity signed by at least 3 responsible Adults including parents and also at least one Police Officer.
The cost of drugs through this system would be peanuts, the list of addicts would be known, the criminals exit the scene because there is no money in it. Would you ads an addict spend $500 on a "hit" from a dealer...or go to your pharmacist and get it legal for $10
?
Governments buy up all source drugs at whatever cost is necessary.
Once existing addicts can get their fix without the criminal element, their habit is sustainable without crime and they can also be enrolled in re-hab.
The producers would get the same returns, because poppy and pot farmers get tiny money for their products anyway....its the Mr Bigs who make all the dough !!
I was once told that the cocaine smuggling trade into US from S.America is so profitable that the dealers figure on losing one twin engine delivery aircraft and its cargoe out of 5...and still make squillions !!