You don't make penalties for the use. It's the abuse.
Everyone that I've ever seen that needed to be fired for their drug use gave ample reason to be fired for their other behavior. If a boss couldn't see that without getting piss samples they aren't much of a boss.
However, I also saw exemplary employees let go because they tested positive for pot use that could have happened a month before the test and not affected their job performance at all.
Well now both you and Techie have come down hard on drug users so we have even more reason to recommend their use. If it prevents people from turning into assholes like you too, maybe we ought to put it in our water supply.
Art