Trump Invokes a 1930s Tariff Law to Hit Canada With 50 Percent Duties

On 20 July 2026, President Trump signed three proclamations invoking Section 338 of the Tariff Act of 1930, a Depression-era statute that had never once been used by a sitting president. The result, according to a White House fact sheet released alongside the signing, is an additional 50 percent tariff on a wide range of Canadian goods, including products that are fully compliant with the United States-Mexico-Canada Agreement. The tariffs take effect on 19 August 2026.

The move lands in the middle of ongoing USMCA renewal talks, and it does so using a legal tool so old that trade lawyers spent the days after the signing re-reading a statute most had never expected to see applied. Fortune was among the first outlets to note the historical significance: Section 338 has sat largely dormant since the 1930s, superseded in practice by newer trade authorities that presidents have preferred because they carry fewer legal uncertainties.

What Section 338 actually allows

Section 338 was written to let the president impose duties of up to 50 percent on a country found to discriminate against American commerce, and in more extreme circumstances to bar its goods from the United States altogether. It was drafted for a trading world of tariff schedules and bilateral treaties, not one built around regional free-trade agreements with dispute-resolution chapters. Using it against Canada, a treaty partner under USMCA, is precisely why the decision has drawn as much legal scrutiny as political attention.

• The tariffs apply to a specified list of Canadian goods, some of which would otherwise cross the border duty-free under USMCA rules of origin.
• The White House has framed the action as retaliation for what it calls discriminatory treatment of American goods and producers.
• The 19 August effective date gives importers roughly a month to adjust supply contracts and inventory before the higher rate applies.
• No comparable action has been taken against Mexico, the other USMCA partner, at least for now.

Why now, and why this statute

The timing places the tariffs squarely inside the USMCA renewal negotiations, which were already tense before the proclamations were signed. Section 338 gives the administration a unilateral lever that does not require the extended investigation periods attached to some of the trade authorities used earlier in Trump's second term. It also sidesteps, for now, some of the court challenges that have targeted other tariff actions, since the statute's text is broad and its case law is thin simply because it has so rarely been invoked.

Nobody in this field has litigated Section 338 in living memory. We are all reading the same seventy-page law review articles from the 1930s trying to work out what a court will do with it now.

Canada's likely response

Ottawa has options that range from formal dispute proceedings under USMCA's chapter mechanisms to retaliatory tariffs of its own, a path Canada has taken before during earlier trade disputes with Washington. Canadian officials have publicly rejected the discrimination framing the White House has used to justify the proclamations, and the renewal talks are now expected to proceed under considerably more strained terms than either side anticipated at the start of the year.

The broader concern voiced by trade economists is less about the specific goods affected than about precedent. If Section 338 becomes a normal tool of the presidency rather than a historical curiosity, USMCA and comparable agreements lose some of the predictability that gives businesses confidence to invest across borders in the first place.

What to watch

• Whether Canada files a formal challenge under USMCA's dispute settlement provisions before 19 August.
• Whether the tariff list expands or narrows in the weeks before the effective date.
• Whether Mexico faces a parallel proclamation as renewal talks continue.
• Whether Canadian industry groups secure carve-outs for specific USMCA-compliant sectors.

Whatever the legal outcome, the choice to reach for a statute this old has already changed the character of the USMCA renewal talks. Both governments now have to negotiate the substance of trade rules while also litigating, in effect, how much of the existing treaty framework the tariff power can simply override.