To really solve the social problems, the sale needs to be legalised.
Making the sale a criminal offence puts money into the hands of organized crime, drives up the prices, forces addicts to steal to buy their drugs and leads drug users to take "worse" drugs like methamphetamine because "better" drugs aren't easily available.
Drugs need to be made legally to ensure quality, to remove harmful impurities, to ensure the dosage is consistent and predictable which reduces risk of overdose, and especially to ensure that when a person consumes "drug A", they do not in fact get a dose of the more addictive/harmful "drug B" (i.e. methamphetamine).
Governments stand to make tax dollars off marijuana too.
There's a trail of logic that must be followed - if it is OK to buy and consume drugs, why is it not OK to sell them?
The only caveat is that methamphetamine should remain illegal to buy or use. The idea being that people will use "less harmful" drugs than methamphetamine because they are available cheap, easy and clean. The strongest possible justification for legalization of sale and use of drugs is to minimize usage and supply of the greatest of all evils - methamphetamine.
We need to accept that people want to get high. You can't arrest that human desire out of existence. We can however remove the harmful effects of criminalization of the sale of drugs.
Criminalization fills prisons, wastes police and legal resources, destroys families, prevents people having functional lives and creates both organized crime and petty crime.
N.B. personally I'm not interested taking in any drugs except alcohol and caffeine so I'm not angling to be able to get high. I wouldn't take em even if they were legal and free.