Washington’s revised Section 338 proclamations took force on September 15, layering 50 per cent duties on top of existing Section 232 metals tariffs for the first time and pushing the combined additional rate on some Canadian steel and aluminum structural goods to 75 per cent. Motorboats, furniture, lighting and printing paper joined the list. Cement, sugar and tissue stock came off it.
OTTAWA, September 16, 2026
A pair of United States presidential proclamations that quietly rewrote the arithmetic of Canada’s most exposed export lines took effect at 12:01 a.m. on Tuesday, September 15, converting what had been a parallel set of tariff regimes into a cumulative one and delivering an effective rate shock to Canadian metal fabricators, furniture makers, boat builders and paper mills that had spent the summer assuming the two programs would never be charged at the same time.
The change is technical, it occupies only a few lines of proclamation text, and it is the single most consequential development in the Canada United States trade file in weeks. Under the original Section 338 proclamations issued on July 20, the 50 per cent additional duties imposed on a defined list of Canadian goods expressly did not apply to articles already carrying duties under Section 232 of the Trade Expansion Act of 1962. That non stacking rule kept aluminum extrusions, steel beams and similar derivative products inside a 25 per cent ceiling. The September 8 proclamations reversed it. As of Tuesday, Section 338 duties apply, in the language of the instruments, in addition to Section 232 duties.
The practical result, according to an analysis published by the Tariff and Trade Task Force at law firm Troutman Pepper Locke, is that aluminum profiles, bars, rods, tubes and pipes newly added to the Section 338 list now face 25 per cent under Section 232 plus 50 per cent under Section 338, for 75 per cent in combined additional duty on top of the ordinary most favoured nation rate. Iron and steel structures, columns and beams land in the same place. For a Canadian extruder shipping architectural profiles into a United States construction supply chain, the landed cost model built in August is now obsolete.
What came on, and what came off
Beyond the stacking reversal, the two Canadian Tariff Modification Proclamations performed a substantial swap of covered goods. The White House characterised the net effect as modest in aggregate terms, saying that products representing roughly 0.6 per cent of United States imports from Canada were being added to the 50 per cent list while goods representing roughly 0.5 per cent were coming off it.
Added to the 50 per cent duty, according to the proclamation annexes, are cheese products including cheddar, Swiss, Emmentaler, Gruyere, Romano, Reggiano, Parmesan, Provolone, blue veined varieties, Roquefort, Edam, Gouda, sheep milk cheese and cheese substitutes; oxidized and dehydrated fats and oils; raw bovine and equine hides and finished leather goods; raw and tanned furskins covering beaver, chinchilla, ermine, lynx, raccoon, sable, fox and wolf; and motorboats and outboard motorboats in specified size bands.
A second annex, issued under the motor vehicle track, adds a far broader industrial list: iron and steel structures, columns and beams; aluminum profiles, bars, rods, tubes and pipes; flexible tubing; hooks, eyes, eyelets, rivets, beads, spangles, buckles, clasps and crown corks; sign and name plates; welding electrodes, wire and rods; seats convertible into beds and a long catalogue of bamboo, rattan, wood, teak, bent wood, plastic and rubber seating along with seat parts, office and kitchen furniture, mattress supports and mattresses; electric table, desk, bedside and floor standing lamps in brass, base metal and non metal finishes, both LED and non LED; golf carts; passenger motor vehicles with engines of 1,000 cc or less; outboard motorboats of 7.5 metres and over; cheese not made from cow milk; paper and paperboard for writing and printing; and fishing rod parts.
Coming off the 50 per cent list are salt and pure sodium chloride, Portland cement, certain chemically pure sugars, toilet and facial tissue stock, bed sheets and similar articles of paper pulp, refined lead, switchgear assemblies, switchboards and certain fishing rod parts. Two alcohol lines also came off the duty schedule: whiskies in containers over four litres and liqueurs and cordials in containers over four litres, both of which are bulk rather than consumer ready formats.
For a Canadian exporter, the swap is not a wash. A cement producer in Quebec and an aluminum extruder in Ontario are not interchangeable businesses, and the relief delivered to one does nothing for the other. What the aggregate percentages conceal is that the burden has been redistributed toward capital goods, construction inputs and durable consumer manufacturing, sectors with longer order books, thinner margins and less ability to reprice in a single quarter.
How the file got here
The current sequence began in July, when the administration issued Proclamations 11046, 11047 and 11048 under Section 338 of the Tariff Act of 1930, imposing 50 per cent additional ad valorem duties on specified Canadian imports following formal findings of trade discrimination in alcoholic beverages, dairy and motor vehicles. Those duties were scheduled to take effect on August 19.
Section 338 is an unusual instrument. Enacted during the Great Depression, it permits the president to impose duties of up to 50 per cent on imports from countries found to discriminate against United States commerce, and, under subsection (b), to exclude goods from importation altogether where the discrimination is maintained or increased after an initial finding. Before this year the provision had never been used to apply tariffs. The National Marine Manufacturers Association, which tracks the file on behalf of manufacturers on both sides of the border, described the July action as the first use of Section 338 in the statute’s history.
Negotiators came close to a deal in the third week of August. Proclamation 11056 suspended the duties for three days, from August 19 to August 22, while talks continued. On August 21 Canada ended the negotiations. Prime Minister Mark Carney said the United States had made late demands that were, in his words, uneconomic and unfair, and that would have undermined the net benefit to Canada and called into question Canada’s ability to conclude trade agreements with other partners. The suspension lapsed and the 50 per cent duties became effective on August 22, applying to roughly $27.6 billion in Canadian goods.
Ottawa answered on August 25. Finance Minister Francois Philippe Champagne confirmed that Canada would match the new United States measures dollar for dollar and rate for rate. Effective September 8, Canada imposed counter tariffs of 15, 25 and 50 per cent on products drawn from those targeted by the American Section 338 and Section 232 actions, with each product’s Canadian rate set to mirror the corresponding American rate. The Canadian list covers $27.6 billion in imports from the United States and is concentrated in steel and aluminum, dairy, appliances, agricultural equipment, pulp and paper, plastics and electronics. Existing counter tariffs, including those on autos, remain in force alongside the new measures.
Alongside the counter tariffs, the federal government announced a $7.5 billion package of new and enhanced supports, layered on top of what Finance Canada described as nearly $25 billion in assistance already provided since the American tariffs began. The package includes $1.5 billion through the Regional Tariff Response Initiative delivered by the regional development agencies, a $500 million liquidity stream under the Business Development Bank of Canada’s Pivot to Grow program, a reduction in the minimum revenue threshold for BDC tariff programs to $1 million, $2 billion through a new Canada Strong Diversification Fund for shovel ready capital maintenance projects, and $3.5 billion in Rapid Response Supports for Workers and Employers, including extended employment insurance flexibilities and a new Worker Retention and Retraining Program.
On September 8 the administration responded to Canada’s retaliation with five further proclamations. Three impose outright import bans on specified Canadian alcoholic beverages, dairy products and motorcycles over 800 cc effective September 29. The other two are the tariff modification instruments that took effect on Tuesday.
The CUSMA question
The most striking feature of the September 15 measures, from a compliance standpoint, is that qualifying under the Canada United States Mexico Agreement provides no relief at all. Section 338 duties and bans apply regardless of whether a good originates under the agreement.
The legal footing rests on 19 U.S.C. section 4512(a)(1), the CUSMA implementing legislation provision stating that no provision of the agreement inconsistent with United States law shall have effect. Section 338 predates the agreement by nearly a century, and the administration has treated that sequencing as decisive. For Canadian exporters, the consequence is severe: origin certification, regional value content calculations and supplier declarations, the entire architecture that has governed duty mitigation on the northbound trade for three decades, deliver nothing against these measures.
The Troutman analysis flags a further structural point. The dairy ban proclamation arises from Canada’s allocation of its cheese tariff rate quota under CUSMA, a matter squarely within the dispute settlement machinery of Chapter 31. The motor vehicle measures likewise concern Canada’s tariff treatment of vehicles under the agreement’s framework. By proceeding under Section 338 rather than through a Chapter 31 panel, the United States has chosen unilateral action over the agreed process. Canada may respond with challenges under both Chapter 31 and the World Trade Organization’s Dispute Settlement Understanding, and the analysis notes that the viability of such challenges will turn on whether Section 338 measures qualify as emergency actions exempt from trade agreement disciplines, and on whether the agreement’s dispute resolution exclusivity provisions are self executing.
That is a live legal question with no settled answer, and it will not be resolved on a timeline useful to a fabricator quoting a job next month.
The boat file as a case study
Recreational marine manufacturing offers a compact illustration of how the September 15 changes reach into a real supply chain.
Under the alcohol scope modification annex, motorboats other than inflatable or outboard motorboats with a length not over 7.5 metres (HTS 8903.31.00), motorboats other than inflatable or outboard with a length over 7.5 metres but not over 24 metres (8903.32.00), and outboard motorboats with a length not over 7.5 metres (8903.93.20) are now subject to the additional 50 per cent duty. Under the motor vehicle annex, outboard motorboats of 7.5 metres and over (8903.99.21) are also captured. The duties apply in addition to any Section 232 exposure and without regard to CUSMA origin.
This is not a peripheral trade. NMMA Canada has told parliamentary committees that the Canadian recreational boating industry exports more than $600 million in product to international markets, with the United States the dominant destination, and the association’s economic impact work has counted roughly 7,000 manufacturing jobs in the Canadian sector within a broader boating economy supporting hundreds of thousands of positions directly and indirectly. The traffic runs both ways: Canada is the largest single customer for American built boats, taking roughly half of total United States boat exports by the association’s count.
The picture on the Canadian side of the ledger is more forgiving. American made recreational boats, personal watercraft and marine engines are not subject to Canada’s September 8 counter tariffs. But a range of marine inputs are. Recreational boat, utility and snowmobile trailers under HTS 8716.39.90 carry 25 per cent. Anchors, grapnels and parts of iron or steel carry 50 per cent, as do stud link, welded link and other chain and chain parts, and certain iron or steel articles used in manufacturing or repairing engines and engine parts for commercial fishing vessels. Non portable stoves and ranges specially designed for use on boats, together with their cooking chambers, top surface panels, door assemblies, burners and other parts, carry 25 per cent.
NMMA Canada has been urging Ottawa to keep recreational boats, marine engines and core marine products out of any future expansion of Canadian retaliation, arguing that in a deeply integrated North American supply chain additional Canadian duties would raise costs for Canadian manufacturers, dealers and marinas as much as for anyone else. The association has also flagged that the breadth of the affected HTS codes pulls in aluminum and fabricated aluminum, steel and fabricated metal, marine electronics and electrical systems, hardware and pumps, seating and furniture, lighting, refrigeration and onboard appliances, and manufacturing tooling. A boat is an assembly of almost everything on the list.
Reaction
Canadian political and business reaction on Tuesday was notably measured, in part because the country’s attention was fixed on a two day investment summit in Toronto rather than on the customs line.
Speaking to reporters at that summit, Carney said that if a mutually beneficial trade arrangement with the White House emerged, Canada stood ready to develop and pursue it. He added a condition: “It has to be one that there’s clear alignment of interests, and a sequencing that is consistent with implementation.” President Donald Trump, for his part, said a trade deal with Canada could be reached fairly soon and characterised Ottawa as eager to sign.
Corporate leaders at the summit largely declined to describe the trade war as a material drag. Bombardier chief executive Eric Martel, whose company has been singled out by the president in recent weeks, said the dispute was not interfering with expansion plans. “We, Bombardier, are creating tens of thousands of jobs in the United States,” he told reporters. “We have a strong presence and we have plans also to invest.”
Linamar chief executive Linda Hasenfratz went further, describing the environment as a source of opportunity for Canadian manufacturers positioned to serve North American reshoring. “We’ve actually been taking advantage of the fact that our customers are on shoring product from Asia and Europe into North America,” she said. “They are happily awarding business to all of Canada, the U.S. and Mexico. And in fact, if I look at the last 12 months, we’ve won record levels of new business for our Canadian plant.” Matthew Bromberg, chief executive of Montreal based flight simulator manufacturer CAE, said the United States remained the company’s largest market and that he was seeing no slowdown in interest on either side.
Those assessments come from large firms with diversified footprints and the balance sheet capacity to absorb a bad year. The exposure profile for a 40 person extruder in southwestern Ontario selling into a single American distributor is different in kind, not just in degree.
Champagne framed the Canadian countermeasures in defensive terms when they were announced. “When the United States asked too much and offered too little, we chose to stand up for Canadians,” he said. “Our dollar for dollar, rate for rate counter tariffs as well as a multi billion dollar support package will protect workers, farmers, families, and businesses as we build a stronger, more resilient, and more diversified Canadian economy.”
Economic reading
Taken at face value, the September 15 changes are small. Adding goods worth 0.6 per cent of American imports from Canada and removing goods worth 0.5 per cent is, in macroeconomic terms, noise against a bilateral goods relationship measured in the hundreds of billions.
That framing misleads in two respects. First, the stacking reversal is not a list change at all. It applies to goods already on the list and doubles or triples their duty burden without adding a single new tariff line. A 25 per cent duty is painful; a 75 per cent duty is, for most fabricated metal products sold into a price competitive American market, prohibitive. There is no margin structure in structural steel or aluminum extrusion that absorbs 75 per cent.
Second, the incidence is concentrated. The affected categories cluster in Ontario and Quebec manufacturing, in British Columbia and Quebec forest products, and in the marine cluster spread across Ontario, Quebec and the Atlantic provinces. These are regional employers in communities without deep alternative labour markets. Aggregate trade statistics will not register what a 75 per cent rate does to a single plant town.
The offsetting force is the one Hasenfratz described. North American reshoring continues to pull work out of Asia and Europe, and Canadian plants with the right capabilities are winning some of it. Whether that current runs stronger than the tariff current is the central unresolved question for Canadian manufacturing this fiscal year, and it will be answered plant by plant rather than in a national number.
What importers and exporters should do now
Trade counsel advising on the September 8 proclamations have converged on a short list of immediate actions, and the guidance applies with equal force to Canadian exporters and to their American customers of record.
- Reclassify against the new annexes. The added and removed lists are specific to HTS subheading and, in the alcohol annex, sometimes to packaging format. A product that was outside the 50 per cent duty on September 14 may be inside it on September 16, and the reverse is also true. Assumptions carried forward from August are unreliable.
- Rebuild landed cost models for stacked goods. Any product potentially subject to both Section 232 and Section 338 needs a fresh calculation at the combined rate. Quotes outstanding at the old rate should be reviewed against contract terms governing duty increases.
- Test whether Canadian sourcing still clears. For some fabricated metal lines the honest answer at 75 per cent will be no, and the alternative sourcing analysis is better done deliberately now than under pressure when a customer moves first.
- Preserve drawback documentation. The September 8 proclamations are silent on whether Section 338 duties are refundable as drawback under 19 U.S.C. section 1313. Until Customs and Border Protection clarifies, importers paying these duties on goods later re exported should retain complete records and take counsel. Goods caught by the September 29 import bans cannot generate drawback at all, because they cannot lawfully enter.
- Use Canada’s remission framework. Ottawa has kept its tariff remission process open to assess requests for exceptional relief from the Canadian counter tariffs, which matters for Canadian manufacturers importing American inputs that have no domestic or third country substitute.
- Do not rely on CUSMA. Origin qualification is not a defence against Section 338. Compliance programs built around preference claims need a second track.
What to watch
Three dates and one question sit in front of the file. September 29 brings the import bans on packaged Canadian alcoholic beverages, whey, molasses, non alcoholic beer and motorcycles over 800 cc, a qualitative escalation from expensive access to no access. Any Canadian legal challenge, whether under Chapter 31 or at the World Trade Organization, will be filed against a backdrop in which the severability clauses in the American proclamations ensure that even a successful challenge to a ban returns the goods to a 50 per cent duty rather than to free entry. And the question underneath all of it is whether the parties return to the table.
Carney’s formulation in Toronto, that any deal must show clear alignment of interests and sequencing consistent with implementation, is a negotiator’s way of saying that Canada will not accept commitments front loaded on its side. Trump’s suggestion that agreement could come fairly soon is not, on the current evidence, supported by anything visible in the proclamation stream. Until that changes, Canadian exporters should plan on the rate they are paying today, and on the possibility that it goes higher.