Does that the DEA will start busting shops that are legal under state law?
Let the 'system' sort them out and see how keen they are.
No, he said that US Attorneys should follow preexisting prosecutorial principles rather than the restraint policy which, in his words, “undermined the rule of law”. [0]
US Attorneys are federal executive-branch political appointees, not state officials whose goals are aligned with the interests of the voters of the state.
[0] http://www.thecannabist.co/2018/01/04/sessions-marijuana-enf...