The rules of the convention were clear, countries who will sign the pact will have to consider marijuana as a Schedule IV drug and there are punishments attached with it. But there are certain articles in the treaty that details about the scientific and medical use of controlled substances. The Department of National Health and Welfare wrote a discussion paper in the year 1979 which was made public in the year 1998
According to the paper, the provisions of the international drug convention make it compulsory for Canada to consider cannabis related activities a punishable offence. As per the obligations illicit trafficking is the only associated behavior. Even if the country considers consumption of this herm as criminal offense, it is not committed to punish or convict such offences.
Cannabis can be possessed by exclusively authorized scientific and medical agencies, in any case agencies can only confiscate unauthorized cannabis possession, there is not regulation or the Canada is not bind to penalize such possession.
There are many loopholes in the framed treaty. Even though member countries are bonded to control the possession of this drug, they cannot take any action against you for consuming it or for possession.