For the same reasons any other substance is regulated, because it can affect other people, see e.g. https://www.cdc.gov/niosh/newsroom/feature/marijuana-and-dri....
In other words: regulation does not itself justify criminalization.
As a compromise the govt heavily taxes legal businesses while allowing the black market to thrive with minimal punishment. C’est la vie.
We might eventually see a variant of tax stamp fraud for marijuana, the way some states do for cigarettes. But that's just the nature of these things, like you said, and I think the general trend is a "win," in terms of eliminating WoD policies.
And meanwhile billions were taken out of the black market, and the government increased tax receipts.
Don't let perfect be the enemy of good (or in the case, 'better').
You're more likely to eat and fall asleep, than to have reduced inhibitions.
High doses can cause underlying conditions to surface, but it's not nearly as destructive as alcohol.
People who get paranoid on THC, are way more belligerent on alcohol.
This is well documented, the above link is one of many.
The fact that how substances are regulated is irregular and inconsistent is a separate issue from whether or not it's ok for a society to regulate some substances.
The bar for "affects others" is extremely low in society.
Unless there's a very clear study, that a certain substance will cause an average human being to be aggressive, belligerent and violent - there's hardly a case for "affects others".
All drug use has risks, including cannabis. But it's been so demonized in the past there's a natural reaction to sweep all concerns away because almost all of them are garbage. Reasonable regulation would be that it's not sold to minors, and that its active ingredients be accurately noted, and that the transaction is taxed appropriately.
It should be legal to sell fentanyl but not as an adulterant. Most of these opioid deaths are due to fentanyl and if they had access to regulated drugs those deaths would be greatly diminished.
My brother died of a heroin overdose many years ago, and I think he might be alive today if the drug he was abusing was at least calibrated for dosage. Maybe not. But it being illegal did not protect him or any of the others lost in the war on drugs.
Edit: To respond to the dead comment below, I think banning alcohol would probably be a good thing. Alcohol exacts a terrible toll on women and children. It’s no surprise, then, that the first thing American women did with the right to vote was ban alcohol. Alcohol is banned in my home country, and many others.
That said, I’m afraid it’s too deeply embedded in western culture to make banning alcohol a realistic possibility. But just because that’s true, how does that justify legalizing and normalizing the new vice of drug use?
Yes, after all this worked so well the first time.
My point is that, even if alcohol prohibition is impractical in a western country, that’s not a reason to normalize and legalize a new and different vice.
If you don't establish such axiomatic foundations in conversations about morality, you're doomed to just talk past each other. For example, I treat free will and empathy as axiomatic goods. I don't like being told what to do, and I don't like harm coming to others. By extension, others having their free will suppressed is bad, but not axiomatically bad in so much as it can cause greater suppression of the freedom of others.
Under such a framework, it should be pretty obvious why I would oppose prohibition. If someone does something that in of itself does not harm others, then that thing is at worst ethically neutral, and thus there is no good to offset the ethical evil of interceding in them doing it. On the other hand, if someone is attempting to kill someone else, or enslave someone else, or otherwise suppress the other's ability to be free, then preventing that by any means necessary is a moral good.
So what are YOUR axioms that you are operating off of? What base assumptions underlie your "moral standards"?