A trade court in the US has blocked Donald Trump from imposing sweeping global tariffs on imports.
A three-judge panel concluded that the US president exceeded his authority when he unveiled additional taxes on foreign-made goods.
Tariffs must typically be approved by Congress - but Trump has argued he had power to act because it was a "national emergency".
The controversial measures unveiled on "Liberation Day" in April, which included a 10% tariff on UK imports, had caused aggressive sell-offs in the stock market.
Minutes after the Court of International Trade delivered its verdict, the Trump administration filed a notice of appeal - meaning the battle could escalate to the Supreme Court.
Several lawsuits have been filed against the president's tariffs - and this ruling relates to a case brought on behalf of five small businesses that import goods from other countries.
The companies, which sell everything from wine to musical instruments, had argued they were struggling to survive because of these additional costs.
The ruling came shortly before Elon Musk confirmed he was leaving his role in the Trump administration.
Trump's deputy chief of staff Stephen Miller criticised the court on social media, writing: "The judicial coup is out of control."
And in a fiery statement, the White House added: "It is not for unelected judges to decide how to properly address a national emergency."
Spokesperson Kush Desai went on to say that trade deficits - where the US imports more from a country than it exports - have "decimated American communities and left our workers behind".
But Oregon's attorney general, Dan Rayfield, welcomed the ruling and described Trump's tariffs as unlawful, reckless and economically devastating.
And Ron Wyden - the top Democrat on the Senate Finance Committee - said the president's actions had "jacked up prices on groceries and cars, threatened shortages of essential goods, and wrecked supply chains for American businesses large and small".
Before the court's intervention, flat tariffs of 10% worldwide were in force - with higher rates for specific countries due to be implemented on 9 July.
Economists had expressed fears that the tariffs could exacerbate inflation, and even cause a recession.
The US dollar strengthened as investors digested the news - with stock market futures also rallying higher.
"We're just trying to work out what it might mean basically but obviously the market is doing a kneejerk reaction so I guess it's reversing a lot of the moves that we've seen," National Australia Bank's head of FX strategy Ray Attrill said.
One of the three judges who heard the case was appointed by the Trump administration, while the other two were named by Ronald Reagan and Barack Obama during their terms in the Oval Office.
Earlier this month, the UK and US agreed a trade deal that would lower tariffs on British cars sold in the US from 27.5% to 10% - and eliminate duties on UK steel and aluminium altogether.
At this stage, it is unclear how the trade court's ruling will affect this arrangement.
(c) Sky News 2025: US trade court blocks Donald Trump from imposing sweeping global tariffs - claimin