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The North American trade fight moved from tariffs to outright bans overnight.
Washington and Ottawa spent the summer trading fifty-percent duties and canceling negotiations, but the mechanism had stayed familiar: higher tariffs on the same goods that kept crossing the border.
That changed on Tuesday, when Canadian counter-tariffs took effect just after midnight and the White House moved to block entire Canadian product lines from entering the US.
President Donald Trump signed five proclamations on September 8, invoking Section 338 of the Tariff Act of 1930 to bar imports of certain Canadian alcoholic beverages, dairy products and motorcycles starting September 29.
A separate set of adjustments added 50 percent duties on Canadian cheeses, motorboats, and further wood, paper and furniture items effective September 15, while removing rock salt and cement from the earlier tariff scope.
The administration framed the move as a reply to Canada imposing “new tariffs on approximately $20 billion in U.S. exports, including steel, dairy, and agricultural equipment,” after breaking off negotiations. The duties apply regardless of USMCA origin status and stack on top of Section 232 tariffs.
Trump also directed the General Services Administration to remove “$50 billion dollars’ worth of Canadian-origin products” from its Multiple Award Schedules, cutting Canadian firms out of long-term federal contracts until Ottawa allows what the White House calls full and fair reciprocity.
Canada’s tariffs triggers response
Canadian counter-tariffs on roughly $20 billion of US goods took effect at 12:01 a.m. Eastern on September 8, with rates from 15 to 50 percent across more than 700 products.
Prime Minister Mark Carney’s government targeted American steel, aluminum, dairy, appliances, agricultural equipment, pulp and paper, machinery and consumer goods, a list built to match Trump’s earlier duties dollar for dollar.
Ottawa paired the package with a 5.42-billion-US-dollar support fund for affected small and medium-sized businesses and workers.
The consumer bite in the US will be uneven. Wisconsin is home to Harley-Davidson’s motorcycle plants and Milwaukee headquarters; Northern border states from Michigan to Washington are the main entry points for Canadian spirits and beer; dairy-producing states will see cheese and whey traffic shift as the September 15 duties bite.
Section 338’s second outing
Section 338 empowers the president to raise duties or block imports from a country deemed to discriminate against US commerce, and carries a 50 percent maximum duty.
The statute had sat dormant since the 1930s and 1940s, last surfacing in a 1949 State Department telegram about Chinese trade, until Trump invoked it on July 20, 2026 to place 50 percent duties on 554 Canadian tariff lines.
Tuesday’s proclamations mark the authority’s second use, and the first to move beyond duties into outright import exclusion.
The alcohol proclamation cites Saskatchewan’s added 50 percent levy on US alcoholic beverages, effective the same day the White House acted, and states that Canada has “maintained or increased the discriminations against the commerce of the United States.”
The 50 percent tariff additions land in importers’ books on September 15. The full import bans follow on September 29.
