Well, the death penalty is already a non-starter in Asgardia, so, there's that.
Most drug prohibition, at least in the U.S., continues because of the monetary benefits the various government agencies at all levels enjoy through the confiscation and selling of personal and real property and the confiscation of cash.
My particular 'drug' of choice is marijuana. But, in the U.S., it's classification as a Schedule 1 drug didn't begin due to any real public threat, but rather to protect the corporate interests of those who were building monopolies in their respective industries. DuPont on the chemical side, and William Randolph Hearst on the textiles side. They both faced a long standing competitor in industrial hemp, marijuana's non-psychoactive cannabis cousin. It had long been used for rope, clothing, paper, oils, food, sails, even sound deadening fabric in early Ford automobiles. It can be made into over 25,000 products. Such a hardy product couldn't be directly attacked so instead DuPont and Hearst funded a smear campaign against marijuana, painting a picture of it as an addictive drug that was destroying the youth of America, even though the head of the AMA at the time testified before Congress that no such epidemic was actually happening and there was no evidence in the medical community that marijuana was dangerous.
The U.S.'s first drug czar, Harry Anslinger, took their smear campaign as gospel and trotted before Congress articles Hearst had published in his own newspapers that were largely racist, and bigoted, towards Mexicans and Africans, and Anslinger even doubled down and threw jazz musicians on the pyre for good measure. Can't have those druggies making the Devil's music corrupting America.
The intended consequence was that cannabis as a whole would be classified on the same level as narcotics, after Anslinger failed to control it via interstate commerce laws, thus rendering industrial hemp a controlled substance as well. They surely succeeded. Industrial hemp farming in the U.S. vanished, nearly overnight, from a height of nearly 2,000 hemp farms having operated at the height, with government subsidizing. It received a short-lived reprieve during the 2nd World War, but was then quickly tossed back on the heap of profit over people, as soon as the need was over.
So, any continued prohibition, at least in the case of cannabis, rests solely on the foundation of hatred, greed, racism, and bigotry. And that's to not even mention all of the health benefits that have finally come out of the shadows over the last three decades or the industrial benefits of hemp production in the textiles industry.