US Supreme Court finally asks: Who really has the power to tax?
In this high-stakes case, even conservative justices signalled scepticism towards Trump’s sweeping tariff authority
THE US Supreme Court hearing on Wednesday (Nov 5) on President Donald Trump’s global tariffs marked a watershed moment in the ongoing debate over executive power. Even conservative justices expressed deep reservations about the administration’s expansive claims of presidential authority.
The case, which represents the first examination by the justices of the underlying legal merits of a piece of Trump’s second-term agenda, has major implications for global trade, the US economy and the wallets of Americans.
At its core, the dispute centres on whether the president can use the International Emergency Economic Powers Act (IEEPA) – a 1977 law designed for national emergencies – to unilaterally impose sweeping tariffs without explicit congressional authorisation.
Trump was the first chief executive to use IEEPA for imposing tariffs when he announced duties on Canada, China, and Mexico in February 2025. The financial consequences are staggering: The federal government collected US$151 billion from customs duties in the second half of its 2025 fiscal year ended September, a nearly 300 per cent increase from that in the same period in fiscal year 2024.
A sceptical court
What made the nearly three-hour oral argument remarkable was the breadth and depth of scepticism from the court’s conservative majority. Chief Justice John Roberts and Justices Amy Coney Barrett, Neil Gorsuch and Brett Kavanaugh all expressed reservations about the administration relying on declared emergencies to issue unchecked tariffs.
Chief Justice Roberts crystallised a central concern when he observed that “the vehicle is imposition of taxes on Americans, and that has always been the core power of Congress”. This framing – emphasising tariffs as taxes rather than merely foreign-policy tools – cuts to the heart of the constitutional question at stake.
Justice Gorsuch raised, perhaps, the most pointed challenge to the administration’s position, warning about a “one-way ratchet towards the gradual but continual accretion of power in the executive branch and away from the people’s representatives”. His concern reflects a broader conservative anxiety about Congress permanently ceding its constitutional powers to the executive branch.
Even more striking, when Solicitor-General D John Sauer conceded that under the administration’s theory, a future president could “very likely” use the same authority to impose sweeping tariffs on gas-powered cars and other products that emit greenhouse gases under a climate change emergency, the implications of such unchecked presidential power became impossible to ignore.
The legal landscape
The administration’s argument rests on asserting that the IEEPA gives the president authority to “regulate” imports during declared emergencies, and that this necessarily includes the power to impose tariffs.
But, as Chief Justice Roberts noted, “The statute doesn’t use the word tariff”.
Justice Elena Kagan put it even more bluntly, telling Sauer: “It has a lot of actions that can be taken under this statute. It just doesn’t have the one you want.”
The case also implicates the court’s “major questions doctrine” – a theory embraced by the conservative majority in recent years, which holds that a president cannot impose a broad policy with huge impacts on society and the economy unless Congress passes a law that specifically allows for it. This is the same doctrine that the court used to strike down former president Joe Biden’s student-loan forgiveness plan.
Lawyer Neal Katyal, representing the businesses challenging the tariffs, emphasised this constitutional foundation. “The idea that every president had this power all along – presidents Reagan to Obama – and none of them knew it and all of them have been spending all this time negotiating with Congress to try and get tariff authority when they had it from the start, is just too fanciful to believe.”
“This court, despite its conservative supermajority and its general deference to executive authority in national security matters, is unwilling to simply rubber-stamp claims of unlimited presidential power when fundamental constitutional principles are at stake.”
Not a unanimous rejection
To be sure, the administration found some support on the bench. Justice Kavanaugh appeared sympathetic, questioning why the law would allow for the imposition of a trade embargo, which may be viewed as an extreme step, as opposed to tariffs, a more targeted punishment.
Justices Clarence Thomas and Samuel Alito also seemed more receptive to the government’s arguments.
Even Chief Justice Roberts himself gave a “crumb of hope” – to quote NBC – to the administration, noting that while tariffs are a tax that is a core power of Congress to impose, they also relate to foreign policy, which the president has full authority over.
Looking ahead
If the court rules against the administration, the practical consequences could be enormous.
Treasury Secretary Scott Bessent, in a court filing in September, said that the US might have to refund US$750 billion or more if the Supreme Court ruled that the tariffs are illegal. Justice Barrett’s questions about the “mess” of potential reimbursements suggest that the court is aware of these complications.
If the court rules against the president over tariffs, it would be the first major legal setback of his second term, marking a significant departure from its general deference to the Trump administration on emergency docket matters.
The broader constitutional question
Beyond the immediate economic impact, this case represents a fundamental test of the separation of powers in the modern administrative state.
The court must decide whether allowing presidents to declare emergencies and then impose taxes – a power explicitly granted to Congress by Article I of the Constitution – represents a dangerous erosion of legislative authority or a necessary tool for executive flexibility in foreign affairs.
Based on Wednesday’s arguments, a majority of the justices appear deeply uncomfortable with the scope of power the administration is claiming.
But oral arguments can be misleading, and the court’s ultimate decision – expected by the end of June 2026 or potentially sooner – may take a more nuanced approach, perhaps placing limits on presidential tariff authority without completely invalidating all of Trump’s actions.
What seems clear is that this court, despite its conservative supermajority and its general deference to executive authority in national security matters, is unwilling to simply rubber-stamp claims of unlimited presidential power when fundamental constitutional principles are at stake.
The question now is whether that scepticism will translate into a historic check on executive authority – or whether the practical realities of foreign policy and the economic consequences of invalidating the tariffs will lead the justices to find a way to uphold, or at least partially preserve, the administration’s position.
