Treaties - fully ratified ones as this one apparently is - have the force Federal statute either directly in the case of self-executing treaties or, in the case of non-self executing treaties, because they compel Congress and draft and the President to sign legislation that comports with the treaty provisions. I've provided the reference elsewhere and don't want to find the link again but look at Article VI paragraph 2. Only the Constitution itself is superior to a signed treaty.
I did a little reading on the subject and as it turns out the treaty referenced by the UN fellow is a non self executing one and our major Federal narcotic laws are written to comply with it. The narcotics schedule came out of that treaty and we basically lifted it whole and plunked it right into our laws.