On 5 November, the US Supreme Court will begin hearing arguments about the legality of President Donald Trump’s tariffs. As important as the tariff issue is, the stakes are much higher than that.

Trump has been claiming  vast powers, at the expense of other branches of government, on the grounds of various “ emergencies”. He has used these claims to justify  sending troops to US cities and  deporting non-citizens without due process under a law dating from 1798.

Trump imposed sweeping global tariffs under the auspices of the International Emergency Economic Powers Act of 1977. Most legal  experts agree, and so far  three lower courts have  ruled, that this act gives him no such power.

This case now presents an important test of the Supreme Court’s willingness to impose limits on Trump’s emergency powers.

The powers Trump is claiming

The US Constitution gives  Congress, not the president, the power to set tariffs. Since the 1930s,  Congress has passed a series of laws granting presidents the authority to adjust existing tariffs and deploy them to protect industries that are crucial to US national security.

The tariffs Trump has imposed this year go beyond the powers any previous president has had.

Some of Trump’s tariffs on goods in specific sectors, such as steel and aluminium, are authorised under Section 232 of the Trade Expansion Act because of their importance to military industries.

But to justify blanket tariff rates on entire countries, regardless of the goods involved, Trump has turned to the  International Economic Emergency Powers Act.

This allows the president to block economic transactions and freeze assets after declaring an emergency. These actions usually target  hostile powers or individuals. An emergency is an “unusual and extraordinary threat” to the US, originating “in whole or substantial part outside the US”.

Trump originally claimed tariffs against  Canada, Mexico and China were necessary to force those countries to stop the traffic in fentanyl, which causes more than 70,000 overdose deaths in the US every year. Yet  less than 1% of the fentanyl that enters the US comes from Canada.

For the “ liberation day” tariffs affecting every other country in the world,  Trump declared the annual US trade deficit in goods constituted “an unusual and extraordinary threat to the national security and economy of the United States”.

This trade deficit has been running since 1976, and it  widened during Trump’s first administration.

The court case

The Trump administration is being sued by a  group of small businesses that have been hurt by the 2025 tariffs, and which claim Trump had no right to impose them. They are supported by a bipartisan  group of legal scholars.

https://youtu.be/p3gW28ntF5A?si=uVyv2wUTX-mqCE1H

Two federal courts and the US Court of International Trade have so far ruled IEEPA  does not give the president the power to set tariffs.

The IEEPA was an amendment to the  1917 Trading with the Enemy Act, which the then president Richard Nixon used to impose 10% import tariffs during a trade crisis in 1971. The Trump administration  has argued that because those tariffs were upheld by courts, Trump’s are also valid.

But the IEEPA, passed in 1977 following  post-Watergate reforms of emergency powers, was intended to limit executive power, not expand it.

In the words of a report from the House Committee on International Relations that underpinned the reforms, “emergencies are by their nature rare and brief, and are not to be equated with normal ongoing problems”.

What will the Supreme Court do?

The weakness of the administration’s legal arguments is reflected in Trump’s public statements about why the Supreme Court must uphold his tariffs. These statements increasingly read like blackmail notes. He has said striking down the tariffs would “ literally destroy the United States of America”.

As well as bringing in billions of dollars in revenue, Trump  claims five of the eight wars he has supposedly ended were thanks to tariff leverage, and “if they took away tariffs, then they’ve taken away our national security”.

Striking down tariffs could be  economically disruptive. It would weaken US leverage in trade negotiations and raise the possibility of large tariff refunds.

These threats may persuade conservative Supreme Court justices who already take an  expansive view of executive power, and who have  so far enabled Trump’s accumulation of it.

However, the one area where Supreme Court conservatives might be willing to limit Trump’s powers is where they interfere with economic orthodoxy.

In a ruling allowing Trump to fire commissioners of  some small, independent agencies, the court also appeared to protect members of the US central bank, the Federal Reserve, because of its “distinct historical tradition”.

The Supreme Court has since temporarily  blocked Trump’s attempt to fire one of the Federal Reserve governors, Lisa Cook. The judges may also decide that allowing a president to impose unlimited new taxes is a step too far.

Even if the Supreme Court does strike down the IEEPA tariffs, Trump is unlikely to abandon tariffs as a policy tool. They are a  core part of his identity.

The administration has already vowed that if it loses in the Supreme Court, it will find other ways to impose tariffs under different laws that “ have the same effect”.

The significance of the Supreme Court’s decision may not be about the tariffs themselves, but about whether it recognises any limit to presidential power.

Disclosure statement David Smith does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Republished from The Conversation, 22 October 2025

The views expressed in this article may or may not reflect those of Pearls and Irritations.