I'm pretty sure that you can still deny someone a job for being a drug user, even if the drugs are legal. In fact, several of those things aren't solved merely by legalization and regulation. Overdoses happen on legal, regulated drugs all the time. A lot of drug related complications are due to mixing substances, which is not solved by legalization or regulation. Clean needles and paraphernalia are not necessarily "solved' by regulation or legalization, clean needles are available right now in any drug store.