Supply Management. Dairy is not a free market in Canada. It is a cartel in which each producer gets a quota. The US complains about it constantly because they massively over-produce dairy, which drops the price of US dairy products, which they then want to export to Canada. It would give us consumers lower prices, but would probably kill our dairy indistry. Or at least that's what we are told. I don't have enough knowledge to say whether that story is valid.