President Donald Trump signed three proclamations on Monday imposing additional 50 percent tariffs on a wide range of Canadian imports, from wine and hockey sticks to cement and dairy products. The measures, which the White House says will cover nearly $20 billion in annual trade—roughly 5 percent of Canada’s exports to the United States—are scheduled to enter into force on 19 August. Crucially, the new duties will apply even to goods that qualify under the United States–Mexico–Canada Agreement (USMCA), removing a shield that had previously protected most Canadian shipments from earlier rounds of tariffs.

The administration invoked Section 338 of the Tariff Act of 1930, a provision unused for nearly a century, to retaliate against what it calls discriminatory treatment of American alcohol, automobiles and dairy products. Washington points to Canadian provincial boycotts of US liquor, a 25 percent retaliatory tariff on non-USMCA-compliant vehicles, and supply-management quotas that limit dairy imports. Viewed from Ottawa, the move is the latest unilateral action in a trade war that began with US tariffs imposed in early 2025, which Canada argues violate the USMCA. The decision follows Washington’s refusal on 1 July to renew the pact in its current form, shifting it to an annual review cycle and injecting deeper uncertainty into North American commerce.

Prime Minister Mark Carney said he and Trump had agreed to “intensify negotiations in the coming weeks,” but warned that Canada is examining “all options” for retaliation if the tariffs take effect. Provincial premiers struck a defiant tone: Ontario’s Doug Ford called for a dollar-for-dollar response, while British Columbia’s David Eby declared there was “not a chance in hell” US alcohol would return to shelves. Economists at major Canadian banks estimate the direct macroeconomic impact is manageable—BMO calculates the targeted goods represent 0.8 percent of GDP—but warn that specific sectors, including chemicals, plastics, electronics and forest products, would be severely hit. The Canadian Chamber of Commerce flagged that roughly 100,000 jobs could be vulnerable.

The 30-day implementation window leaves room for legal challenges and diplomatic off-ramps. Trade lawyers note that Section 338 has never been tested in court and may face litigation. Meanwhile, US and Mexican negotiators are holding a third round of bilateral talks this week, with Canada largely sidelined. The next factual milestone is the 19 August deadline, by which the tariffs will take effect unless negotiations yield a breakthrough or the administration alters course.