How did the U.S.–Canada trade war escalate from fentanyl tariffs to Section 338 duties?
The conflict moved through successive legal tools rather than one uninterrupted tariff. The initial IEEPA tariffs were narrowed for USMCA-compliant goods and later invalidated by the Supreme Court, but Section 232 duties remained and a Section 122 surcharge replaced the lost IEEPA charge. When the United States then declined to renew USMCA at its review, it invoked Section 338 for 50 percent duties on selected Canadian goods. A brief deadline pause did not yield an agreement, so those duties took effect. To assess exposure, distinguish USMCA treatment and the legal authority behind each tariff rather than assuming the IEEPA decision ended the dispute.
Trace the chain
The opening measures
- 1Trump’s opening threatAnnouncement
President-elect Trump vows a 25 percent tariff on everything from Canada and Mexico
Three weeks after the election, Trump posted on Truth Social that one of his first-day executive orders would put a 25 percent tariff on all products from Canada and Mexico, to stay in place until the two countries stopped drugs, especially fentanyl, and migrants crossing into the United States. It was the opening move of a trade war with a partner that had a free-trade agreement Trump himself had signed in 2018.
The White House ·
President Trump promised in November to “sign all necessary documents to charge Mexico and Canada a 25% Tariff on ALL products coming into the United States, and its ridiculous Open Borders.”
Why it matters here. Trump’s pledge of a first-day tariff order moved the dispute from a threat to the formal tariff-and-response stage recorded next.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
- 2IEEPA tariffs imposedRegulatory
Trump signs the IEEPA order: 25 percent on Canada, 10 percent on energy; Trudeau answers with C$155 billion
Using the International Emergency Economic Powers Act and a declared fentanyl emergency, Trump ordered a 25 percent tariff on Canadian goods with a 10 percent rate for energy, to take effect February 4. Prime Minister Justin Trudeau announced 25 percent counter-tariffs on C$155 billion of American goods: C$30 billion immediately and C$125 billion after 21 days.
The White House ·
Until the crisis is alleviated, President Donald J. Trump is implementing a 25% additional tariff on imports from Canada and Mexico and a 10% additional tariff on imports from China. Energy resources from Canada will…
Why it matters here. The IEEPA order and Canada’s announced C$155 billion answer established the broad tariff coverage that the next step narrowed for qualifying goods.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
- 4Steel and aluminum dutiesResponse
Section 232 steel and aluminum tariffs hit; Canada matches with C$29.8 billion
The restored 25 percent Section 232 tariffs on steel and aluminum applied to Canada, the largest supplier of both. Ottawa answered dollar for dollar from March 13 with 25 percent tariffs on C$12.6 billion of steel, C$3 billion of aluminum and C$14.2 billion of other goods including tools, computers and sports equipment, on top of the C$30 billion already in force.
Department of Finance Canada ·
Following a dollar-for-dollar approach, Canada is imposing, as of 12:01 am, March 13, 2025, 25 per cent reciprocal tariffs on a list of steel products worth $12.6 billion and aluminum products worth $3 billion, as well…
Why it matters here. The restored Section 232 duties and Canada’s C$29.8 billion match added a separate tariff track as the legal challenge to IEEPA reached the Supreme Court.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
The IEEPA reversal
- 5Supreme Court hears caseLegal
Supreme Court hears the consolidated tariff cases and sounds skeptical of the government
After granting certiorari on September 9 and expediting the cases, the Court heard nearly three hours of argument in Learning Resources v. Trump and Trump v. V.O.S. Selections. Solicitor General John Sauer argued that regulating importation plainly embraces tariffs; Neal Katyal for the businesses and Oregon's Benjamin Gutman for the states argued that IEEPA never mentions tariffs, duties or taxes. Justices across the spectrum pressed the government to point to statutory text authorising tariffs.
SCOTUSblog ·
The Supreme Court on Wednesday seemed skeptical of President Donald Trump’s authority to impose sweeping tariffs in a series of executive orders earlier this year. During more than two-and-a-half hours of oral…
Why it matters here. After hearing the consolidated tariff cases and sounding skeptical of the government, the Court proceeded to decide whether IEEPA authorized the tariffs.
IEEPA Tariff Refunds: From the Supreme Court Ruling to the Console Lawsuits
- 7Canada’s tariff resetLegal
The Supreme Court strikes down the IEEPA tariffs; the 35 percent goes, a Section 122 surcharge and the 232 tariffs stay
In Learning Resources v. Trump the Court held 6 to 3 that IEEPA does not authorize tariffs, ending the 35 percent fentanyl tariff on non-USMCA goods and the 10 percent energy rate. The relief for Canada was limited: about 90 percent of its exports were already exempt, the Section 232 tariffs on steel, aluminum, autos and lumber were untouched, and Trump replaced the lost tariffs with a Section 122 global surcharge from February 24 that exempted CUSMA-compliant goods.
Osler, Hoskin & Harcourt ·
On February 20, the U.S. Supreme Court determined that the International Emergency Economic Powers Act (IEEPA) does not authorize the President to impose tariffs. The 6-3 decision in Learning Resources Inc., et al. v.
Why it matters here. With the 35 percent tariff gone but the Section 122 surcharge and Section 232 tariffs still in place, trade pressure remained active as the required USMCA review approached.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
USMCA and Section 338
- 8USMCA extension declinedRegulatory
USMCA joint review: the United States declines to renew the agreement
At the six-year review required by the agreement, the three countries met virtually and the United States refused to confirm a 16-year extension, leaving USMCA in force but on annual reviews and putting its future on the negotiating table. Canada and Mexico both backed extension. Greer said the U.S. would keep working with both to address the agreement's shortcomings and the trade deficits.
Office of the U.S. Trade Representative ·
In accordance with the Agreement, the United States, Mexico, and Canada met virtually today to discuss the operation of the USMCA. The United States did not agree to renew the USMCA in its current form. As a result…
Why it matters here. The U.S. refusal to confirm USMCA’s 16-year extension left the agreement unresolved, setting the stage for a unilateral Section 338 tariff action.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
- 9Section 338 revivedRegulatory
Section 338, unused since 1930: three proclamations for 50 percent tariffs on autos, alcohol and dairy-linked goods
Trump revived Section 338 of the Tariff Act of 1930, which lets a president impose up to 50 percent duties on a country that discriminates against U.S. commerce, and signed three proclamations targeting Canada's auto tariffs and quotas, the provincial bans on American alcohol and the cheese tariff-rate quotas. Unlike the fentanyl tariffs, the duties applied regardless of USMCA origin, covering goods from wine to hockey sticks to cement, and were to take effect in 30 days. Carney said Canada had merely matched U.S. measures and was ready to intensify talks.
The White House ·
Today, President Donald J. Trump signed three Proclamations pursuant to Section 338 of the Tariff Act of 1930 to impose additional 50% tariffs on certain goods of Canada in response to Canada’s discriminatory treatment…
Why it matters here. The three proclamations for 50 percent duties created a deadline for the announced tariffs, which Trump temporarily paused while claiming a deal.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
- 11Deadline talks collapseAnnouncement
Talks collapse at the deadline: Carney walks away from 'a bad deal'; Greer says Canada declined to finalize
Minutes before midnight Carney suspended negotiations and recalled his team, saying last-minute U.S. changes were unfair and uneconomic. He later named the sticking points: no tariff relief for trucks and a dispute over Canadian content in vehicles, U.S. language restricting Canada's other trade deals, and demands touching French-language and cultural protections. Greer said the deal on the table cut steel, aluminum, auto and lumber tariffs and that Canada had walked back commitments.
Prime Minister of Canada ·
As a result, this evening, I have decided to suspend trade negotiations with the U.S. and have directed Canada’s negotiators to return to Ottawa.
Why it matters here. Carney’s decision to suspend negotiations and the U.S. account that Canada declined to finalize left the announced 50 percent duties to take effect.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
- 12Fifty percent duties beginRegulatory
50 percent tariffs take effect on about $20 billion of Canadian goods; Carney: 'they asked too much and offered too little'
The Section 338 duties started at midnight on roughly $20 billion of exports including wine, furniture, dairy, cement, clothing and hockey equipment, about 4 percent of what Canada sells to the United States. At a press conference Carney promised dollar-for-dollar retaliation from September 8, concentrated in steel, dairy, appliances, farm equipment, pulp and paper and electronics, and when asked why it felt like going to war, said 'because we were attacked'. The Canadian dollar fell on Monday.
CNBC ·
The U.S. imposed 50% tariffs on some Canadian products on Saturday after trade talks between the two countries fell apart on Friday.
Why it matters here. The duties’ entry into force ended the brief Section 338 pause after negotiations failed to yield a finalized agreement.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
What pushes back
- 3USMCA goods exempted
Two days in, USMCA-compliant goods are exempted after the automakers call
After Ford, GM and Stellantis executives lobbied the White House, Trump amended the orders so that goods qualifying for USMCA preference paid no tariff, energy and potash outside the agreement paid 10 percent, and everything else paid 25 percent. The exemption, which covered roughly 90 percent of Canadian exports, defined the shape of the fentanyl tariffs for the next year.
The White House ·
Today, President Donald J. Trump announced adjustments to tariffs imposed on imports from Canada and Mexico in recognition of the structure of the automotive supply chain that strives to bring production into America.
What it pushes against. Exempting goods that qualified for USMCA preference pushed against a fully across-the-board IEEPA tariff, even as the next escalation targeted particular industrial sectors.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
- 6IEEPA authority rejected
Supreme Court holds 6 to 3 that IEEPA does not authorize the President to impose tariffs
Chief Justice Roberts wrote for the Court in Learning Resources v. Trump: the taxing power belongs to Congress, and when Congress has delegated tariff authority it has done so explicitly and with limits, so IEEPA's words regulate and importation cannot carry a delegation of unbounded tariff power. The Federal Circuit was affirmed and the D.C. district-court case was sent back to be dismissed for lack of jurisdiction. By then CBP had collected roughly $166 billion in IEEPA duties from about 330,000 importers on 53 million entries, all of it now potentially refundable.
Supreme Court of the United States ·
Fulfilling that role, we hold that IEEPA does not authorize the President to impose tariffs.
What it pushes against. The Court’s holding removed IEEPA tariff authority, pushing against escalation by ending the legal basis for the Canada-specific 35 percent charge recorded next.
IEEPA Tariff Refunds: From the Supreme Court Ruling to the Console Lawsuits
- 10Brief deal pause
Two hours before the deadline, Trump pauses the tariffs three days: 'we have a DEAL!'
With the 50 percent duties due at 12:01 a.m. on August 19, Trump posted that they were paused for three days because the two countries had a deal subject to finalizing documents. A proclamation said Canada had committed to remove the alcohol, dairy and vehicle measures. Carney's statement said substantial progress had been made with important work still to do, and confirmed the postponement to end of day August 21.
PBS News (Associated Press) ·
President Donald Trump said Tuesday he was delaying the 50% U.S. tariffs on $20 billion worth of Canadian imports after the two countries reached a last-minute deal less than two hours before the sanctions were to go…
What it pushes against. The three-day pause pushed against immediate escalation, but it lasted only until the deadline at which the talks failed to produce a finalized agreement.
The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
Changes to this chain
- Proposal #136 accepted (verify:v2): why of step 12 -> The duties’ entry into force ended the brief Section 338 pause after negotiations failed to yield a finalized agreement.
- Proposal #44 accepted (verify:v1): why of step 12 -> After talks collapsed, the 50 percent Section 338 duties took effect on roughly $20 billion of Canadian exports.
Timelines in this chain
- The US–Canada Trade War: From the Fentanyl Tariffs to Section 338 and Dollar-for-Dollar Retaliation
- IEEPA Tariff Refunds: From the Supreme Court Ruling to the Console Lawsuits
- The Fed's Rate Path: From the 2024 Cuts to Warsh's First Meetings
- Record Beef Prices: The Smallest Herd Since 1951, the Packer Probe and the Import Fix
A chain is written by the editor from entries already published on the timelines above, each of which was read against its source before publication. The chain changes when those entries do. Data and terms.