I predicted this long before Trump was a thought in the minds of most voters. Instead, people went partisan and defended the Administration especially one apologist made up a whole host of excuses. If cannabis was rescheduled it would be difficult to change it in light of the fact that before a change could be made the actual uses and addictive potential relative to other substances would have to be demonstrated, something very hard to undo, even by Sessions, and millions would have standing then.
The process is that the HHS calls for the latest scientific and medical state of the art information on cannabis. There are two criteria for a drug to be on the C-I list, and one is that there be no recognized medical use. Well, hell, epilepsy to mention only one thing is without doubt appropriately treated by cannabis. The addiction potential exists but it is lower than the opiates/opioids. In my professional estimation (certified NY medical cannabis health professional here among other things) the likely category ought to be C-IV, where most benzodiazepines are. This not only permits wide-ranging research and therapies but the harshest penalties under law both federal and state are for C-I and then C-II.
BTW, the HHS does not have to be the one to instigate this, a request can be made to the HHS sec by the AG who shall (note shall) follow the above procedure. The findings of the HHS and recommendation for rescheduling are binding on the AG who SHALL make the changes. This is not optional. This is not an executive order, this is an act provided for by the Controlled Substances Act. Congress does not have a veto power as they have approved it already under the Act. The CSA was created so we would be compliant with the international treaties on controlled substances and is completely consistent with it.
The only excuse is a lack of moral courage. Obama should have requested this process be implemented in his first term and we would not be having this problem at least as far as the draconian legal penalties and denial of treatment to those in need. Can he ORDER them to do so? No, but Presidents choose those who are of a like mindset and as this is a completely legal and ethical request their denial would be problematic to say the least.