In those states making marijuana legal, do employers in those states still get to screen for drugs? A person smokes legal weed and becomes unemployable for a whole range of jobs. And then, of course, the worker problem becomes worse and you need more immigrants. It is almost like a conspiracy. Also, how many companies will flee states where drug use is legal?
In the 1800s the British used drugs to win a lot of China, and it worked. America better be careful.
DOT regs. Federal requirement. If you're going long-haul you can't get around that.
Drilling companies won't hire a druggie, either. Most companies which have jobs involving moving expensive equipment won't either.
The list is long, but there is no Right to work somewhere if you are a drug user. (I suppose they'll sue for that next.)
In which case, more productive industries will leave states like the gun manufacturers are leaving anti-gun states. Insurance costs and liability profiles will mandate it.
I am sure for many jobs (such as trucking) Federal statutes take precedence, so pot smoking is still a no-no.