The escalation has arrived. At 12:01 a.m. ET on August 22, the United States imposed an additional 50% tariff on a broad range of Canadian goods under Section 338 of the Tariff Act of 1930, a provision Washington had barely used in decades before this year. Even the date carries a story. The tariffs were originally set to take effect August 19, then pushed three days after a last attempt at trade talks between Washington and Ottawa collapsed.
Three separate proclamations carry this action, each with its own annex spelling out precise HTS codes rather than broad category names. The targeted sectors are motor vehicles and automotive products, alcoholic beverages (tied to longstanding US complaints about provincial liquor board restrictions), and dairy, plus a long tail of additional goods swept in along the way, including cement, furniture, fishing rods, seeds, clothing, wigs, wooden tableware, and hockey equipment. Energy, potash, fish, critical minerals, and anything already covered under Section 232 metals tariffs are carved out.
Every prior round of tariffs on Canada, going back to February 2025, carried some form of exemption for goods that qualified under USMCA. That protection is gone. The guidance on these proclamations is explicit, the tariffs apply to covered goods regardless of whether they qualify for USMCA preferential treatment. A valid certificate of origin, something that has reliably shielded compliant importers through a year and a half of tariff actions, does nothing here.
This did not come out of nowhere. USMCA has a built in six year joint review clause, and that review came due July 1, 2026. Rather than agree to extend the agreement in its current form, the US Trade Representative announced it would not renew, citing what it called shortcomings and a persistent trade deficit with Canada and Mexico. Three weeks later, on July 20, the three proclamations were signed. The administration has framed the tariffs as a response to what it describes as discriminatory or unequal treatment of US commerce, not as a national security matter, and that distinction matters for the legal footing underneath all of it.
That footing is actually one reason this round looks more durable than what came before it. In February 2026, the Supreme Court struck down the tariffs the administration had built on the International Emergency Economic Powers Act, the authority behind most Canada and global tariff actions since early 2025. Section 338 is different. Congress explicitly delegated tariff authority under it for cases of discriminatory treatment, which gives this round firmer domestic legal ground than the emergency powers route the courts just rejected. That does not mean it is beyond challenge. Trade law analysis has flagged a real conflict with USMCA’s Article 2.4, which bars raising duties on originating goods, along with likely issues under WTO rules on most favored nation treatment and bound tariff rates. No legal challenge had been filed as of the effective date, but the exposure is definitely worth watching.
Ottawa has said it will match the new US tariffs dollar for dollar, and counter tariffs covering $27.6 billion in US goods take effect September 8. Steel and aluminum go to 50%, matching the US rate. Dairy sees 25 to 50%. Pulp and paper, plastics, agricultural equipment, electronics, textiles and apparel, and wood products all get hit at rates between 25 and 50% depending on category, on top of the auto tariffs Canada already had in place
Canada is Wisconsin’s largest export market by a wide margin, buying $7.5 billion in Wisconsin goods in 2025, 28% of everything the state shipped abroad. Wisconsin’s top exports, machinery, computer and electronic products, transportation equipment, chemicals, and food products, line up closely with categories now caught on one side of this fight or the other. An escalating tariff war with the state’s number one customer is not an abstraction here, and it is not a small one either.
Impacted customers should pull the annexes for all three proclamations and check your Canadian origin goods against the actual HTS codes listed, not just the category names, since the coverage runs deeper than cars, alcohol, and dairy implies. Stop treating a USMCA certificate of origin as protection against this specific tariff, because it is not. If you also export to Canada, map your outbound goods against Canada’s new counter-tariff list before September 8. And if any of this touches your entries, bring it to our team now rather than after an audit flags it, since the cost of guessing wrong here runs 50% deep.