I believe Ssmmoking is right on this one. It would not be very easy to just flip a switch to unwind what the states have passed. There is a process that has to be followed and it would take a long time. Probably a moot point anyway. The DOJ has bigger fish to fry then snuffing out the MJ flame.
Oh and WI is now moving on medical MJ...the train continues to pick up steam.
No, I think you don't understand law or the power of the fed. He doesn't need to unwind California law. He has the full power of the FBI, DEA and ATF at his disposal. He can send them in, raid the largest producers, arrest the owners and charge them with a felony all without California's help. Here, read this article and you'll understand what's at stake. http://www.politico.com/magazine/story/2016/12/jeff-sessions-coming-war-on-legal-marijuana-214501