When the US government made various “common” drugs illegal (marijuana, cocaine, etc.), did they include a grandfather clause letting people who already owned the substances keep them legally? If not, what happened to the stuff? Surely there were people out there sitting on mounds of the stuff when it was eventually made illegal, right?
While on the topic, do Coke bottles from the 1800s (when it still had cocaine) still exist, and are they legal to possess?
Usually the laws involved purchase or sale of the substance. If you had it and didn’t try to sell it, you did nothing illegal.
The hard part would be proving you bought it when it was still legal, however.
Generally, most of the drugs didn’t just become illegal overnight. In the case of Marijuana, it became (de facto) illegal to produce and sell decades before it actually became illegal to posses. With things like cocaine and opiates that had medicinal uses, they first ceased to be over-the-counter, then eventually they just stopped writing prescriptions for them. So by the time all of these actually became illegal to posses, chances are the legally-aquired stockpiles of the stuff was pretty much gone.
In the case of prohibition, there was the huge loophole that though it was illegal to produce, sell or transport alcohol, it was not illegal to posses or drink it. So you could definitely still sit on your stockpile.
I’m not sure about the coke bottle-- that’s a good question.