Revised U.S. Section 338 tariff lists take effect today, adding Canadian cheese, structural steel, aluminum, furniture and ATVs while dropping road salt and cement, and for the first time letting 50 per cent duties stack on top of Section 232 metals tariffs
Ottawa, September 15, 2026 | Peacock Tariff Consulting Canada Trade Desk
As of 12:01 a.m. Eastern this morning, the list of Canadian goods facing 50 per cent U.S. tariffs under Section 338 of the Tariff Act of 1930 has changed shape. Two presidential proclamations signed on September 8 and taking effect today remove a handful of politically sensitive products from the duty lists, including rock salt, Portland cement, toilet tissue stock and refined lead, and replace them with a much longer roster of new targets: cheddar, gouda and other cheeses, raw hides and furskins, iron and steel structural beams and columns, aluminum profiles and tubing, office and household furniture, mattresses, electric lamps, golf carts, small-engine passenger cars, motorboats, writing paper and fishing rod components.
The product reshuffle is significant on its own. But the more consequential change buried in the same proclamations is a single clause reversing the administration’s earlier “non-stacking” rule. Under the original July 20 proclamations, goods already subject to Section 232 national security tariffs were exempt from Section 338 duties. From today, Section 338 duties apply “in addition to” Section 232 duties. For Canadian aluminum and structural steel products newly added to the lists, that means combined additional duties of 75 per cent above the normal most-favoured-nation rate, according to an analysis by the law firm Troutman Pepper Locke. It is the highest effective tariff rate ever applied by the United States to a broad category of Canadian industrial goods.
What changed today
The White House framed the modifications as fine-tuning. In a fact sheet issued September 8, the administration said the president was “modifying the July 20, 2026 actions by removing certain products, such as rock salt and cement, from the scope of the Section 338 tariffs and replacing those products with new ones, ranging from all-terrain vehicles (ATVs) to additional dairy products,” in order “to offset the burden to U.S. commerce while better serving the public interest.” The removals are widely read as a response to domestic pressure: northern U.S. states rely heavily on Canadian road salt heading into winter, cement is a construction input in short domestic supply, and toilet tissue stock feeds U.S. paper mills.
The additions are broader and more strategic. According to Troutman Pepper Locke’s breakdown of the two modification proclamations, the alcohol-linked proclamation (amending Proclamation 11046) now sweeps in cheddar, Swiss, Emmentaler, Gruyere, Romano, Reggiano, Parmesan, Provolone, blue-veined cheese, Roquefort, Edam, Gouda, sheep’s milk cheese and cheese substitutes; oxidized and dehydrated fats and oils; raw bovine and equine hides and leather goods; raw and tanned furskins including beaver, chinchilla, lynx, raccoon, sable, fox and wolf; and motorboats of certain sizes. Removed from that list are whiskies and liqueurs in containers over four litres, the bulk formats used for U.S. bottling and blending.
The motor-vehicle-linked proclamation (amending Proclamation 11048) reaches even further from its nominal subject. New 50 per cent targets include iron and steel structures, columns and beams; aluminum profiles, bars, rods, tubes and pipes; flexible tubing; hardware such as hooks, rivets, buckles and crown corks; sign plates; welding electrodes and wire; convertible sofa beds; seating made of bamboo, rattan, wood, plastic and rubber; office, kitchen and other furniture; mattress supports and mattresses; table, desk, bedside and floor lamps in brass, base metal, LED and non-LED formats; golf carts; passenger vehicles with engines of 1,000 cc or less; outboard motorboats of 7.5 metres or more; cheese not made from cow’s milk; writing and printing paper and paperboard; and fishing rod parts. Removed are salt and pure sodium chloride, Portland cement, certain chemically pure sugars, toilet and facial tissue stock, paper-pulp bed sheets, refined lead, switchgear assemblies and switchboards.
A third modification covering the dairy proclamation (11047) was referenced in the September 8 dairy import ban proclamation but had not been separately published as of Troutman’s September 14 update. Customs brokers should expect it to appear in the Federal Register with its own effective date.
The stacking clause
The reversal of the non-stacking rule is the change most likely to reshape Canadian supply chains. When Section 338 duties were first proclaimed in July, each proclamation stated that the duties “shall not apply to articles subject to duties pursuant to section 232.” That carve-out mattered because Canadian steel and aluminum have faced Section 232 tariffs since 2025, currently at 25 per cent for aluminum and, for most steel, 50 per cent following the June 2025 doubling. Under the original rule, a Canadian aluminum extrusion facing the 232 tariff could not also be hit with a 338 duty.
The September 8 modification proclamations delete that protection and state that Section 338 duties “shall apply in addition to” Section 232 duties. Troutman’s analysis identifies two immediate categories of exposure: aluminum profiles, bars, rods, tubes and pipes, which now face 25 per cent under 232 plus 50 per cent under 338 for a combined 75 per cent; and iron and steel structural products such as columns, beams and fabricated structures, which face a similar combined burden. The White House fact sheet confirms the policy in plain terms, stating that the Section 338 tariffs “apply in addition to tariffs imposed under Section 232 of the Trade Expansion Act of 1962.”
“Importers who had structured their supply chains around the original non-stacking rule should reassess their landed cost models and consider whether continued sourcing from Canada remains economically viable for affected products,” the firm wrote in its client alert. For Canadian structural steel fabricators and aluminum extruders that had adapted to the 232 regime over the past 18 months, often by absorbing part of the duty or shifting to higher-value fabricated products, the stacked rate effectively prices them out of the U.S. market for the affected tariff lines.
No CUSMA shelter
A second structural feature of today’s measures is that CUSMA origin provides no relief. The White House fact sheet states that the Section 338 tariffs “apply to all covered goods regardless of whether a good originates under the U.S.-Mexico-Canada Agreement (USMCA).” Troutman’s lawyers note that Section 338 predates the trade agreement by nearly a century, and that the USMCA implementing legislation, at 19 U.S.C. 4512(a)(1), provides that no provision of the agreement inconsistent with U.S. law shall have effect. The result is that CUSMA qualification, historically the primary duty-mitigation tool for Canadian exporters, does nothing against Section 338 duties or the import bans scheduled for September 29.
That has legal as well as commercial implications. The dairy proclamation arises from Canada’s allocation of its cheese tariff-rate quota under CUSMA, a matter the United States has previously pursued through CUSMA Chapter 31 dispute panels. The motor vehicle proclamation concerns Canada’s tariff treatment of U.S. vehicles under the CUSMA framework. By choosing Section 338 rather than Chapter 31, Troutman observes, Washington “is proceeding with unilateral measures rather than USMCA dispute resolution.” Canada retains the option of challenging the measures under both Chapter 31 and the WTO Dispute Settlement Understanding, though the firm cautions that the viability of such challenges “will turn on whether Section 338 actions constitute ’emergency’ measures exempt from trade-agreement disciplines.”
How we got here
Section 338 authorizes the president to impose duties of up to 50 per cent on goods from any country found to discriminate against U.S. commerce, and under subsection (b) to exclude those goods entirely if the discrimination is “maintained or increased” after an initial proclamation. The provision had never been used in the modern era until July 20, when the Trump administration issued Proclamations 11046, 11047 and 11048 targeting Canadian alcohol, dairy and motor vehicle practices respectively. The duties were scheduled for August 19, suspended for three days by Proclamation 11056 after Canada signalled it would address the practices at issue, and then activated on August 22 when talks collapsed.
Canada’s response came on September 8: surtaxes of 15, 25 and 50 per cent on more than 700 U.S. tariff lines covering roughly C$27.6 billion (US$20 billion) of imports, with each rate matched to the U.S. rate on the equivalent Canadian product. Finance Canada’s list doubled existing surtaxes on U.S. steel and aluminum to 50 per cent and added dairy, appliances, agricultural equipment, pulp and paper and electronics. The same day, Trump signed the five proclamations whose second phase takes effect today. The first phase, the import bans on Canadian packaged alcohol, whey and molasses products, non-alcoholic beer and motorcycles above 800 cc, follows on September 29.
The White House fact sheet was explicit about the political logic. “Over the past year and a half, only two countries have chosen to retaliate against President Trump’s tariffs rather than negotiate a deal with the United States: The People’s Republic of China and Canada,” it said, adding that the actions “further safeguard American workers from Canada’s discriminatory or unreasonable and unequal practices.” U.S. Trade Representative Jamieson Greer described the measures as a “natural consequence of Canada’s continued discriminatory treatment of crucial American exports.”
Ottawa’s response
Canada-U.S. Trade Minister Dominic LeBlanc called the September 8 package “unjustified” and said the government was assessing its impact. “Our first priority remains on protecting and supporting Canadian workers, farmers, families, and businesses from these unjustified actions,” he said in a statement reported by CBC News. LeBlanc said he remains in contact with Greer and that “when the U.S. is ready to engage, our government will work in good faith and constructively towards a more secure mutually beneficial trading relationship that fully respects Canadian sovereignty.”
Prime Minister Mark Carney, speaking to Bloomberg on Monday, said Canada is “ready to sit down” for a deal that respects its red lines on sovereignty, culture and the freedom to sign other trade agreements, and that he welcomed President Trump’s weekend comment that an agreement could come “fairly soon.” He gave no indication that Ottawa would suspend its own counter-tariffs as a precondition. Finance Minister Francois-Philippe Champagne told The Associated Press the government has “the wherewithal to support our industries, to support our workers for as long as it takes, with whatever it takes.”
Ottawa’s support architecture now includes a C$7.5 billion package announced alongside the counter-tariffs and a C$1.5 billion top-up to the Regional Tariff Response Initiative delivered by the seven regional development agencies. The Canadian Federation of Independent Business has argued that the programs, which recently lowered their access threshold to C$1 million in revenue, still exclude roughly half of the small business community. CFIB estimates 53,112 Canadian businesses are directly affected by the U.S. tariffs, the Canadian counter-tariffs or both, with affected firms reporting median added costs of about C$65,000 a month.
Sector impacts
Steel and aluminum. The stacking clause lands hardest here. Canadian structural steel fabricators, who supply beams, columns and pre-engineered building components to U.S. construction projects, and aluminum extruders supplying window, curtain-wall and industrial profiles, now face a 75 per cent combined additional duty on the affected lines. Given that the integrated North American metals market already saw disruption from the 2025 Section 232 measures and Canada’s September 8 doubling of its own surtaxes on U.S. metals, analysts have warned of materials being taxed multiple times as they cross the border in different stages of fabrication.
Dairy. The cheese additions extend the U.S. dairy campaign from tariff-rate quota policy into the product market. Canadian specialty cheese exporters, a small but high-value segment concentrated in Quebec and Ontario, face a 50 per cent duty on their principal U.S. export lines from today, with whey and molasses products banned outright from September 29. The forthcoming dairy scope modification could widen the list further.
Furniture and home goods. The addition of office, kitchen and household furniture, seating, mattresses and lamps brings a sector that was largely outside the July lists squarely into the dispute. Canada’s furniture industry is concentrated in Quebec and southern Ontario and exports the majority of its production to the United States. Economists tracking the dispute have flagged furniture, along with dairy and alcohol, as the categories where U.S. consumers will see the sharpest price effects because substitute supply takes months to scale.
Recreational vehicles and boats. ATVs, golf carts and larger motorboats join the lists today; motorcycles above 800 cc face an outright ban in two weeks. Canada’s powersports and marine manufacturing sector, with major plants in Quebec, is heavily export-dependent.
Hides, furskins and leather. These additions reach into the agricultural and trapping economy, including Indigenous and northern harvesters who sell raw furskins into U.S. auction markets.
Beneficiaries of the removals. Canadian producers of road salt, cement, tissue stock, refined lead and switchgear see their 50 per cent duty lifted as of today. For salt producers in Ontario and Nova Scotia and cement plants across the country, the timing ahead of the winter and fall construction seasons is significant, although the reprieve is at the president’s discretion and could be reversed.
Compliance priorities for Canadian exporters
Exporters and their U.S. importers of record should treat today as a hard reset of their tariff classification review. Every Canadian-origin product shipped to the United States should be re-checked against the annexes of the two modification proclamations at the ten-digit HTSUS level, since several additions and removals are defined by container size, engine displacement, vessel length or material composition rather than by broad heading. Goods that were compliant on Monday may be dutiable at 50 per cent today, and goods that were dutiable may now be clear.
For metals, landed-cost models built on the July non-stacking rule are obsolete. Exporters should confirm with U.S. customs brokers how Section 232 and Section 338 duties will be sequenced on entry summaries and whether Section 232 derivative-product treatment interacts with the new 338 lines. Troutman notes that the proclamations are silent on drawback, leaving open whether Section 338 duties can be recovered on goods later re-exported from the United States; importers should preserve full documentation pending guidance from U.S. Customs and Border Protection.
For goods on the September 29 ban lists, the proclamations’ transitional rule provides that goods imported but not yet entered for consumption or withdrawn from warehouse before that date remain subject to the 50 per cent duty rather than the ban. Exporters with product already in U.S. bonded warehouses or foreign trade zones have a two-week window to enter it. Goods arriving after September 29 will be refused entry. The severability clause means that even a successful court challenge to a ban would snap the affected goods back to the 50 per cent duty, not to duty-free treatment.
Canadian importers of U.S. goods should not assume today’s U.S. changes trigger any corresponding adjustment to Canada’s September 8 surtax list. Finance Canada has said individual rates are set to match U.S. rates on corresponding goods, so the U.S. product additions could in principle prompt Canadian additions, but no such change has been announced. Remission applications remain the main avenue for relief where U.S. inputs have no practical substitute.
Outlook
Today’s modifications tell two stories at once. The removals show an administration responsive to domestic cost pressure in specific categories, which suggests that further targeted carve-outs are possible if U.S. industries lobby effectively. The additions and the stacking clause show an administration willing to escalate the economic pressure on Canada even as the president talks publicly of a deal “fairly soon.” For Canadian businesses, the second story is the one that governs planning. Until a revised negotiating text appears, the operating assumption should be that the tariff wall is higher today than it was yesterday, that it will be reinforced by import bans in two weeks, and that CUSMA offers no shelter from either.