President Trump imposed 50 percent tariffs on a broad range of Canadian goods Monday night, signing three proclamations that target motor vehicles, dairy and alcohol under an obscure 1930 trade-discrimination law that has not been publicly used since 1949. The White House said the duties take effect in 30 days and apply to Canadian imports including wine, cement and hockey sticks, whether or not they are covered by the U.S.-Mexico-Canada Agreement.

The action marks the sharpest escalation to date in a trade fight that has simmered since Trump returned to office in January 2025, and locks in a legal workaround after the Supreme Court struck down his global tariff regime this year. It also cracks open the free-trade zone Trump himself negotiated and signed in 2018, exposing goods that had moved duty-free to a rate that under the invoked statute cannot go higher.

Three proclamations

Each proclamation cites what Washington calls unfair treatment in a specific sector, senior administration officials said in a call with reporters. On cars, the White House points to a Canadian tax on U.S. motor vehicles and parts that fall outside USMCA, calling the levy "unreasonable" and discriminatory. On dairy, the proclamations target Canada's long-running supply-management system, which imposes tariffs of up to 300 percent on imports above set quotas. On alcohol, they cite the enduring provincial boycott of American spirits that most Canadian provinces imposed last year and have refused to lift while U.S. metals and auto duties remain in place.

The new duties "apply to all covered goods," regardless of USMCA coverage, one official said. Energy, potash, critical minerals and fish are exempt. "Canada has to be held accountable for this continued discrimination," the official said.

A 1930 law

The proclamations rely on Section 338 of the Tariff Act of 1930, a provision that lets the president impose duties of up to 50 percent on countries found to be discriminating against U.S. commerce. Attorneys John Veroneau and Catherine Gibson of Covington and Burling LLP, in a 2016 review of the statute, found no public record of its use since 1949.

The choice reflects the administration's search for legal footing after the Supreme Court in February struck down the sweeping global tariffs Trump had imposed under the International Emergency Economic Powers Act of 1977, ruling that he had exceeded a president's authority under a law reserved for national emergencies. In recent weeks Trump has used Section 301 of the Trade Act of 1974 to justify a 25 percent duty on Brazil that takes effect Wednesday. Section 338, unlike either, is aimed at discrimination rather than emergencies, and remains untested in modern court.

Ottawa's response

Prime Minister Mark Carney said Canada was ready to "intensify" trade talks with Washington in the coming weeks. In a statement posted to X, he called the action "the latest in a series of unilateral US trade actions that began with the US imposing a series of tariffs in direct violation of the Canada-United States-Mexico Agreement," and cited "threats to Canadian sovereignty," a reference to Trump's repeated calls to annex Canada as the 51st state.

Ontario Premier Doug Ford took a harder line, writing on X that "If these tariffs proceed, Canada should respond tariff for tariff, dollar for dollar." Canada last year imposed a 25 percent counter-tariff on about C$30 billion in U.S. goods, some of which Carney has since removed. It maintains 25 percent duties on selected U.S. steel, aluminum and vehicles.

Stacking on existing barriers

Monday's tariffs land atop a wall of duties already in place. The U.S. maintains tariffs of 15 to 50 percent on Canadian steel, aluminum and copper; 35 percent on softwood lumber; and 25 percent on non-U.S. parts in cars. The administration earlier this month declined to renew USMCA in its current form, opting to keep the pact alive through a rolling series of annual reviews.

The administration did not officially link the new tariffs to Canadian wildfires, though the president wrote on Truth Social last week that pollution costs from Ontario blazes "must of necessity be added to the TARIFFS Canada is currently paying." One senior official said the 50 percent tariffs are not related to the wildfires, adding that Trump "has asked for options on that."

Grudge or gambit

Michael Devereux, a University of British Columbia economics professor, told the BBC the move marks "a significant escalation because it directly targets goods that were previously exempt under the US, Canada, Mexico trade agreement that President Trump negotiated and signed himself in 2018." Devereux said he doubted the tariffs were a negotiating tactic and would "rather see this as just an impulsive move that came from kind of a grudge that the US government and President Trump has against Canada."

The 30-day window sets a clock on both governments. Candace Laing, head of the Canadian Chamber of Commerce, urged officials to make "meaningful progress" in talks before the duties take effect. Chris Swonger, head of the Distilled Spirits Council of the United States, warned the decision "raises the risk of further retaliation." Whether Ottawa and Washington use the month to bargain or to prepare fresh countermeasures will decide whether Canadian wine, hockey sticks and cement become the next test of how far Trump's second-term tariff project can travel through the courts.