I was really confused by all this and I could not understand the mechanisms that could even exist to put up trade barriers between provinces. I recently watched a TVO #OnPoli podcast that cleared it up a bit for me. These barriers are not explicit ones like tariffs or other inter-provincial taxes. They are things like having different requirements of a “first aid kit” in each province, so if you want to sell them, you have to consider 12 possibly contradictory standards. They are impedance that comes up incidentally, but while trying to meet some other end. There aren’t [necessarily] provinces intentionally trying to put up trade barriers. They are just managing their own affairs, and these minor barriers are an inevitable consequence of having provincial power at all.
Show this post to your therapist.