Marijuna, ok. Heroin and cocaine? No way! This can't be good for the society. This two are heavy drugs and mayn other crimes are related to them. And what about juveniles taking this drugs freely? I don't think this a good idea.
Back in 2000 I campaign for liberalization, sadly, we only got drug use decriminalized and 15 years after that liberalization still hasn't happened.
The big change you can see and I lived through it, is not with hashish use but with hard drugs, specially heroin, back in 2000 we had a heroin epidemic, everyone had a case or two in the family, if not in family a close friend or a neighbor.
After decriminalization those people were sent to treatment, not prison, needle exchange in every pharmacy, and all that good stuff.
Everyone caught with some kind of illicit drug had to undergo a few months of psychological consultations with a specialist, I was never caught but a lot of my friends went there, you can say it's a waste of resources because we only smoked a few joints and there are people with serious drug and alcohol addiction who could use that time, but it served as prevention, none of my friends ever became an heroin addict.