The world has shifted it's thinking on Cannabis in the last decade.  It is now considered on par with alcohol in terms of danger to users.
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It is the UN resolution that requires updating.  I'm sure there can be an interim exception while the UN reviews the effects of amending the resolution.  If the UN does not recognize the relative harmlessness after sufficient time then Canada can withdraw from the treaties.  International law moves at a turtles pace.  It's an important issue but hardly hypocritical to disagree with this one aspect while calling for enforcement of a ban on chemical weapons.