WASHINGTON – U.S. President Donald Trump’s key tool for deploying tariffs will face a critical legal test in the Supreme Court on Wednesday — one which could upend his plans to realign global trade.
In a post on social media, Trump called the hearing “one of the most important in the History of the Country.”
The top U.S. court will hear from states and businesses that argue Trump’s use of a national security statute to hit nearly every nation with tariffs goes beyond the powers of the president.
Trump used the International Emergency Economic Powers Act of 1977, known as IEEPA, for his so-called “Liberation Day” tariffs and fentanyl-related duties on Canada, Mexico and China.
The U.S. Constitution gives power over taxes and tariffs to Congress. Jeffrey Schwab of the Liberty Justice Center, which is representing small businesses in the hearing, has said Congress would not have intended to hand unrestricted powers to the president. IEEPA does not include the word “tariff” or any of its synonyms.
“The president says that he can impose tariffs on any country, at any rate, at any time, for any reason. That essentially means that he’s saying IEEPA is a blank cheque,” Schwab said in a call with journalists last week. “That can’t be what IEEPA means.”
The president has argued that if he is not allowed to use IEEPA for tariffs, the United States “will be at a major disadvantage against all other Countries throughout the World, especially the ‘Majors.’” Trump posted on social media Sunday that it would leave America defenceless and cause “the ruination of our Nation.”
“The only people fighting us are Foreign Countries who for years have taken advantage of us, those who hate our Country and, the Democrats, because our numbers are insurmountably good,” Trump posted.
White House press secretary Karoline Leavitt said Tuesday that the Trump administration is confident in its legal arguments and optimistic the court will “do the right thing.”
The Supreme Court justices will have to consider the language in IEEPA, particularly wording about the president’s “power to regulate importation,” said Tim Brightbill, a partner in Washington-based Wiley Rein LLP’s international trade practice and a professor at Georgetown University’s law school.
Trump’s team is arguing the power to impose tariffs is clearly encompassed in that phrase, while the lawyers for the businesses and states say Congress delegates tariff authority and IEEPA was never intended for wide-ranging duties.
Justices will also consider the major questions doctrine — a legal principle requiring clear congressional authorization on issues economically or politically significant — and the non-delegation doctrine, a principle that prohibits Congress from ceding its legislative power to other branches of government.
If IEEPA were to allow for tariffs, Brightbill said, the court would also consider whether Trump’s use of the duties actually deals with the emergencies he’s citing.
The president hit most of the world with so-called “reciprocal” tariffs after declaring an emergency over trade deficits. Experts and economists have pushed back, saying trade deficits do not constitute an emergency.
Trump hit Canada with 25 per cent economywide tariffs in March by declaring an emergency at the northern border related to the flow of deadly fentanyl. These tariffs don’t apply to goods compliant under the Canada-U.S-Mexico Agreement on trade, known as CUSMA.
U.S government data shows a minuscule volume of fentanyl is seized at the northern border compared to the United States’ border with Mexico.
Despite a significant response from Ottawa to address Trump’s fentanyl concerns, the president boosted those duties to 35 per cent in August as trade negotiations between the two countries deteriorated.
Prime Minister Mark Carney seemed to steady bilateral relations during a White House visit last month — but Trump again suspended negotiations after Ontario sponsored a TV ad quoting former president Ronald Reagan criticizing tariffs. Trump threatened an additional 10 per cent duty and claimed Canada was trying to influence the Supreme Court ahead of the hearing Wednesday.
That ever-shifting tariff threat on Canada would end if the court rules against Trump’s use of IEEPA, but Leavitt said “the White House is always preparing for plan B.” Trump has other tools he could deploy in his quest to realign global trade, but they would require more restraint.
America’s top court could have until June to issue a ruling but it’s expected to come much sooner.
The Supreme Court’s decision will not affect Trump’s expanding use of tariffs under Section 232 of the Trade Expansion Act of 1962 — tariffs that are already hammering Canada’s steel, aluminum, automobile, lumber and copper industries.
“There are clearly a variety of other tariff tools in the tool box and it seems quite clear to me that tariffs are a cornerstone of this administration’s economic policy,” Brightbill said.
“And so, they are most likely very ready to pivot to another strategy or strategies if the court rules against these IEEPA tariffs.”
This report by The Canadian Press was first published Nov. 5, 2025.
