We were discussing this aspect. William Barr has announced he wants to get out of the Marijuana enforcement business. If the Feds legalize marijuana, will the states where it is currently illegal individually have to vote to make it illegal?
Yes,
A similar issue has been arising with Hemp based food/supplement products. The federal government legalized hemp based products back in a farm bill in December, allowing for growing, production, and manufacture- basically they completely removed it from all drug schedule lists and reclassified it as a food product.
However, many States still have hemp listed as the same schedule as cannabis even though they aren't the same plant (cousins) hemp has a tiny fraction of THC (pretty much almost undetectable, something along the lines of .003% versus cannabis is around 10% or more), very antiquated laws in some states were vague and said 'any trace of THC' makes it the same classification.
This is causing a crap load of issues in Texas right now because Hemp-based CBD sellers in some cities (Tyler, North Richland Hills) are being targeted by police even though it is federally legal, it is questionable under Texas law. However, most of the cities in the State are following federal law and allowing sales (hell, our mayor's wife sells it here).
The Texas Legislature is working now to try to clarify this and remove hemp completely to stop the ambiguity. Unfortunately, there are still some drug-warrior Ned Flanders types trying to block it acting like hemp is heroin.