Section 338: the never-used 1930 tariff law, explained

What does Section 338 actually do?

Section 338 is a provision of the Tariff Act of 1930 — the statute better known as Smoot-Hawley. It allows the president to impose duties of up to 50 percent on goods from a country found to discriminate against US commerce. The trigger is a judgment about a trading partner's behaviour toward American products, not a declared emergency.

Has it ever been used before?

Not to impose tariffs. Trade lawyers who have gone through the provision's history place the last invocation of Section 338 of any kind at around 1949, and can find no public record of duties ever actually being levied under it. The July 2026 proclamations against Canada are, as far as the public record shows, the first time in the law's ninety-six years that it has been used to put a tariff into effect.

Why does the 50% rate matter?

Because it is the ceiling. Section 338 caps the duties it authorises at 50 percent, so the rate announced against Canada is not a midpoint or an opening position — it is the statutory maximum, applied immediately and in full. That leaves the administration no room to escalate under this instrument without switching to a different legal authority.

How is this different from the administration's other tariffs?

Most of this administration's tariffs — and most of the litigation against them — have rested on emergency powers, where the central legal question is whether an emergency actually exists. Section 338 rests on different ground: it turns on whether a foreign country discriminates against US commerce, a question about trade practice. Whether that footing proves more durable in court is genuinely unknown, for the straightforward reason that nobody has ever tested it.

The proclamations also sit apart from the administration's Section 232 national-security duties in a practical way: goods already covered by Section 232 measures are excluded from the new Canadian tariffs.

What did the July 2026 proclamations cover?

Three proclamations, signed July 20, 2026, impose 50 percent duties on Canadian motor vehicles, alcoholic beverages and dairy products, effective 30 days after signing — around August 19. The affected product lists run well past the three headline categories, covering items from wine to hockey sticks to cement, and reach goods that had been protected under the USMCA. Excluded: energy products, potash, fish, critical minerals, and goods already subject to Section 232 duties.

The White House's stated grievances are specific: 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 (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.

One thing the proclamations do not mention: wildfire smoke. The Fold reported on July 19 that the president had threatened tariffs while blaming Canada for smoke drifting south, and noted that no instrument in US trade law prices transboundary smoke into a tariff. The proclamations bear that out — the legal case is built entirely on autos, alcohol and dairy.

What happens next?

Collection begins around August 19, and the 30-day delay leaves Ottawa a window to respond. 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 — so a 50 percent duty on that trade is a charge on a shared supply chain rather than on a foreign industry alone. The open legal question is whether Section 338's discrimination footing survives a court challenge; because the provision has never been used, there is no precedent either way.