The doctrine of States' rights is presupposes federal supremacy and a legalistic viewpoint. Marijuana can't be a State's rights issue because it's a federal issue. This is why you often hear the states' rights advocates call for a smaller federal government - states rights can only flourish without the shadow of federal jurisdiction.
Right now marijuana is illegal federally - all States' rights proponents acknowledge this. The old policy of being hands off but reserving the right to bring the iron fist down on otherwise legal businesses was a bad policy. The uncertainty and risk profile killed a lot of investment - to this day, the tax burden on pot businesses is insanely high because they're not permitted to deduct business expenses related to growing/distributing marijuana because those activities are federally illegal.
Thankfully, Sessions is legalistic. If congress got off their butts and legalized it/returned the legality decisions to the state, Sessions would surely respect their decision.
I enjoy marijuana more than most and I suppose Sessions enforcing the law - it's a bad law and collectively we need the motivation to make it better. This legal twilight zone is complete bogus - bring it into the open and drive out the criminal element and let the best organization flourish.