Alcohol is a drug too.
When legalised, most dealers will fall apart and might give jobs to people.. but how do you control people's dosis? Only with education and more deep prevention schemes other than just limit the amount of drugs one could buy..
Have you seen joe rogan and johann hari talk about it. trust me you'll enjoy it. it first interested me.Depression is also a big issue everywhere and if you can go somewhere to buy hard stuff like cocaine/heroine you can easily just commit suicide without further ado..
This is far more complex honestly.. legalizing would help to destroy kingpin's empires but what do you do with the junkies?