You have to be a fool as a lawyer to speculate on this, so allow me to be a fool.
Probably if you've been acquitted in another country as a Canadian or permanent resident charged with trafficking in that country and you return to Canada, first of all, it's unlikely that prosecutorial exercise in Canada would be used to prosecute you again. If it did happen, and if you had a good defence lawyer, you can enter the plea of autrefois acquit.