It’s worth noting that the U.S. Supreme Court is notorious for reversing decisions of the 9th Circuit Court of Appeals. If Antonin Scalia was still alive, I’d think it probable in this case. Now, I’m not sure.
But this isn’t really the battle. I’ve always seen medical marijuana laws as something of a gateway to full legalization and, in the meantime, a loophole that would be exploited to its fullest (which is probably another reason—see here for what I think is the main one—why law enforcement types right up all the way to the executive branch are so dead set against them).
Paul Elias and Gene Johnson, “Court Bans Feds From Prosecuting Medical Marijuana Cases If No State Laws Broken,” Talking Points Memo, August 17, 2016, Court Bans Feds From Prosecuting Medical Marijuana Cases If No State Laws Broken