There are various mechanisms that are clearly outlined within the treaties themselves, and I'm sure Professor Hoffman can speak to this as well, by which the treaties can be modernized. Amendments can be tabled and they are then either accepted or subject to a conference of the parties, or they are rejected.
Modification is a mechanism of the scheduling of particular drugs, so the drugs are placed in a particular schedule, rather like—I'm not sure how the Canadian system works—but the schedule they're placed in determines how strictly those particular drugs are regulated and controlled. Cannabis could potentially be rescheduled from schedule 1 down into a less strict schedule that might make it more accessible in some ways, or it could be de-scheduled and actually removed altogether from the treaties. It's not entirely impossible.