What is a failure is legalizing the use of drugs. You're getting into the technicalities.
When you lower law enforcement surrounding addictive drugs to a state where it's basically equivalent to legalizing drugs and you take this action independent of other actions like treatment and other stuff, you get net bad effects to society.
When you lower law enforcement surrounding addictive drugs to a state where it's basically equivalent to legalizing drugs and you take this action independent of other actions like treatment and other stuff, you get net bad effects to society.