look for this symbol when you buy dairy in canada.
so long as this is maintained, as a consumer, i would be less concerned about import and export taxes collected by the state. i would just avoid american dairy by checking the labels.
i actually suspect that canadian dairy may develop a market in the united states on the basis of it being additive free if there was a more open market and it were labelled that way. it's a powerful selling point. however, the supply management remains essential to the canadian dairy industry and can't be up for negotiation.