No matter what the physiology is, enforcement gets real damned interesting for an employer disciplining you for participating in a legal activity on your own time. With the substance being illegal in the first place, enforcement is a pretty simple matter. With it legal in some places and not others, it gets a little more problematic. I think the interaction between the federal and state governments on this issue will be worth watching.
Personally, I don't particularly care if it is legal. I just don't want to be out working on MV gear with an electrician or operator that isn't fit for duty.