How a 1930 trade law put 50% US tariffs on Canadian goods

At 12:01 a.m. Eastern Time on Saturday 22 August 2026, the United States began charging an additional 50% duty on a long list of Canadian products. The measure covered roughly US$20 billion of trade and rested on a legal provision that had sat unused for generations. Hours earlier, Canada’s prime minister, Mark Carney, had suspended negotiations and called his negotiators home.

What took effect

President Donald Trump signed three proclamations on 20 July 2026, each finding that Canada discriminated against American commerce in a particular area: alcoholic beverages, dairy products and motor vehicles. The tariffs were originally due to start on 19 August, reflecting a 30-day notice period in the law. On 18 August the president postponed them by three days, to 22 August.

Although the proclamations named three sectors, the lists of goods attached to them went much further. According to an analysis by the law firm Covington & Burling, they included chemicals, prepared food and beverages, plastics, metal items, machinery, cosmetics, wood and paper products, industrial equipment and electronics. The Canadian law firm Gowling WLG put the affected trade at about 5% of Canada’s exports to the United States.

Two features made the duties bite. They applied on top of most other tariffs, and they applied even to goods that qualify for duty-free treatment under the United States-Mexico-Canada Agreement (USMCA), the pact Canadians call CUSMA. Goods already subject to separate national-security tariffs, such as steel, aluminium and cars, were initially left out.

What Section 338 is

Section 338 of the Tariff Act of 1930 allows a president to impose duties of up to 50% on products from a country found to discriminate against US commerce compared with its treatment of other countries. If the discrimination continues, the president may go further and block imports altogether.

A report by the Congressional Research Service (CRS), the US Congress’s non-partisan research arm, said this was the first time a president had expressly cited the statute to impose tariffs. Covington noted that the provision had effectively lain unused for more than 75 years and had never been tested in US courts.

The administration turned to it after losing a broader tool. The CRS report recalls that in February 2026 the US Supreme Court ruled, in Learning Resources, Inc. v. Trump, that the International Emergency Economic Powers Act does not authorise a president to impose tariffs. Since then, the report says, Washington has relied on other statutes.

Why Canada was targeted

Two of the three Canadian measures at issue were themselves responses to earlier US tariffs. Canada had imposed a 25% tariff on certain US vehicles, and most provincial liquor boards had stopped selling American alcohol. The proclamation on alcohol argued that this disadvantaged US producers because the provinces had applied no similar restrictions to drinks from other countries.

The third complaint was older. Canada manages its dairy industry through production quotas and import limits, a system known as supply management. The dairy proclamation said Canada let retailers obtain import quota for European cheese under its trade deal with the European Union but not under the equivalent quota for US cheese.

There was also a wider backdrop. According to the Canadian law firm BLG, the United States declined to renew USMCA in its current form at the agreement’s first joint review on 1 July 2026. The pact remains in force but is now subject to annual reviews.

How the talks collapsed

The gap between the July announcement and the August start date was widely read as a negotiating window, and senior Canadian officials travelled repeatedly to Washington. On 18 August Trump said the two countries had reached a deal and delayed the tariffs to allow it to be finalised, Covington reported.

It was not. Late on 21 August Carney announced that Canada was suspending the talks. BLG quoted him as saying the United States had proposed new terms that were “unfair, uneconomic, and called into question the reliability of any deal”, and, the following morning, that Washington had “asked too much and offered too little”. He said the late demands touched on Canada’s relations with other trading partners, its car industry and its protections for culture and the French language.

The US account differed. Gowling WLG quoted the US Trade Representative, Jamieson Greer, as saying Canada had “declined to finalize the trade deal under the terms agreed earlier this week”.

Canada’s response

On 25 August the Canadian government announced that it would match the US measures “dollar for dollar, rate for rate”. Counter-tariffs of 15%, 25% and 50% would apply from 8 September to US goods worth C$27.6 billion, concentrated in steel, dairy, appliances, agricultural equipment, pulp and paper, and electronics. Ottawa also announced a C$7.5 billion package of support for affected workers and businesses.

Why it matters

The episode showed that a US administration could still raise steep tariffs quickly after the Supreme Court’s ruling, using a statute with few procedural hurdles. It also showed that qualifying under the regional trade agreement no longer guaranteed duty-free access to the US market.

Covington warned of “a material risk of further escalation”. It noted that Canada’s retaliation had so far avoided more sensitive areas such as restrictions on exports of energy and critical minerals, and that Trump had threatened to raise tariffs on Canadian cars, trucks, automotive parts and steel to 50% from 1 January 2027.