Supply management is the trade barrier Canadian politicians are reticent to tear down

Open this photo in gallery: Cows in a dairy farm in Granby, Que. on Feb. 5. U.S. President Donald Trump has threatened to impose tariffs on Canadian dairy products.Christinne Muschi/The Canadian Press As the United States presses Canada for dairy market access, federal and provincial leaders will have to decide whether it's worth protecting supply management, a system that's been an irritant with trading partners and a trade barrier within the country. U.S. President Donald Trump threatened on Friday to impose tariffs on Canadian dairy within days after complaining that supply management is unfair to American dairy farmers. (Canada imposes…