The attorney general must follow the direction of the president. Given Trump’s inconsistent statements on the subject, Trump could probably go either which way, so prohibitionists would need to convince him the counter-strike is a good idea. While that possible, the attorney general will face the same conundrum that Eric Holder was faced with, which is the state laws of possession and home growing cannot be reversed, and they don’t have the budget to raid stores in a meaningfully effective way.
According to Tenth Amendment Center, “Americans for Safe Access calculates that a direct raid on a medical marijuana dispensary costs around $300,000 and investigative costs run about $12 million per raid… The annual DEA budget runs about $2.87 billion. It wouldn’t take too many investigations and raids to wipe that out. In fact, shutting down all the dispensaries in Denver alone would cost more than twice the total DEA budget.” If a lawsuit to shut down the regulation of stores was successful, consumers will turn to the black market, so there will be more dealers, dealing to more underaged teenagers, making an even better argument to keep legalization.