Trump imposes 50% Canada tariffs under Section 338, a 1930

President Trump imposed 50 percent tariffs on a broad range of Canadian goods on Monday, signing three proclamations covering motor vehicles, alcoholic beverages and dairy products. The duties take effect 30 days after signing, around August 19. The White House said they answer what it called Canada’s discriminatory treatment of American products.

Why it matters

Section 338 has sat on the books for ninety-six years without ever being used to impose a tariff; trade lawyers reviewing its history place the last invocation of any kind around 1949. That matters in two ways. The provision caps duties at 50 percent, so the headline rate is not an opening position — it is the ceiling the statute allows, taken in full, which leaves no room to escalate without switching instruments. And it rests on different legal ground from the emergency powers that have carried most of this administration’s tariffs and drawn most of the litigation: Section 338 turns on whether a foreign country discriminates against US commerce, a question about trade practice rather than about whether an emergency exists. Whether that proves more durable in court is untested, for the straightforward reason that nobody has ever tested it.

The measures exclude energy products, potash, fish, critical minerals and goods already subject to separate Section 232 duties. They do reach goods that had been protected under the United States-Mexico-Canada Agreement, and the affected product lists run well past the three headline categories, covering items from wine to hockey sticks to cement.

The administration’s stated grievances are specific. It cites a 25 percent Canadian tariff on US motor vehicles in place since April 2025; provincial restrictions on American alcohol, with all but two provinces and territories having halted purchases and retail sales of US alcoholic beverages, which the White House says cut those imports by 81 percent; and dairy tariff-rate quotas it argues treat American producers worse than European ones.

The instrument is the genuinely unusual part. Section 338 of the Tariff Act of 1930 — the statute better known as Smoot-Hawley — allows the president to impose duties on a country that discriminates against US commerce. It has never before been used to impose tariffs. Trade lawyers who have gone through its history put the last invocation of the provision at all at around 1949 and can find no public record of duties ever actually being levied under it.

The same provision caps those duties at 50 percent. The rate announced on Monday is therefore not a midpoint or a bargaining number but the maximum the statute permits, applied immediately and in full.

The Fold reported on July 19 that Trump had threatened tariffs against Canada while blaming it for wildfire smoke drifting south into the northern United States, and noted then that no instrument in US trade law prices transboundary smoke into a tariff. Monday’s proclamations bear that out. Smoke appears nowhere in them: the legal case is built entirely on autos, alcohol and dairy, and whatever role the smoke complaint played in the politics, it did no work in the paperwork.

Canada is the largest single-country export market for American goods, and the two economies are unusually integrated in autos, where parts routinely cross the border several times before a finished vehicle is sold. A 50 percent duty applied to that trade is therefore a charge on a shared supply chain rather than on a foreign industry alone. The thirty-day delay before collection begins leaves Ottawa a window to respond.

Trump imposes 50% Canada tariffs under Section 338, a 1930 law never used before

Sources