Complicated issue. I think drugs like coke, heroin, meth... these are suicidal to ingest, and murderous to provide.
I think legalizing "kaneh bosm" [cannabis] is appropriate, it should be regulated like alcohol and tobacco [it is a seeded plant, and Torah is clear about seeded plant eligibility for use]. If someone drives while stoned, there should be laws akin to drinking and driving. With mj in the black market kids have far greater access [big problem]. Here in California mj is nearly legal, and society is near unchanged [except black market criminals are raking in the dough, I think co-ops which remove the money making factor may be prudent]. Israel has an up and coming medical marijuana program as well. - The actual smoking, I think, is a bad way to ingest anything, tobacco or otherwise, and should be abstained from to refrain from damaging a persons lungs/body. Eating pot, or "vaporizing" it brings no wear and tear to the body.
I think the laws regarding drugs like coke and the like should have much higher penalties than there currently are. I think all crimes are too under-punished [murder, rape, assault and battery, embezzling, etc.]. Perhaps people who are addicted to hard drugs should face a rehab like prison instead of just being detained in prison; I don't know.
One could use the seeded plant argument on opium as well... it is tough to come to a Torah based reason to prevent opium ingesting... although an hour on Youtube looking at opium addicts provides logical reasons to make it illegal.
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Ultimately one needs to decide on what quality of life one is going to lead. One has a choice; to rely on outside stimulation to be happy, or to generate happiness from the inside out. Whatever the choice one makes, one needs to make the choice in a way that only affects the individual.