Tensions are rising between Canada and the U.S. after President-elect Donald Trump threatened to impose steep tariffs on Canadian goods. Now, a top official in Canada, Doug Ford, the Premier of Ontario, is warning that Canada might retaliate by shutting down its energy exports to the United States.

Ford has made it clear that if Trump moves forward with his plan to slap a 25% tariff on Canadian imports on his first day in office, Canada won’t sit idly by. “We will go to the extent of cut...