The US Supreme Court blocked a crucial instrument that the president has used to push his economic agenda on Friday, ruling that Donald Trump overreached himself in enacting a broad set of tariffs that disrupted international commerce.

The International Emergency Economic Powers Act (IEEPA), according to the conservative-majority high court’s 6–3 ruling, “does not allow the President to impose tariffs.”

Trump has always used tariffs as a tool for negotiations and pressure, but when he took office again last year, he deployed emergency economic powers in a way never seen before to impose fresh tariffs on almost all of the US’s trade partners.

These comprised distinct sets of charges aimed at key allies Mexico, Canada, and China over immigration and illegal drug flows, as well as “reciprocal” tariffs over trade practices that Washington considered unfair.

With IEEPA, “Congress would have done so expressly, as it consistently has in other tariff statutes,” the court said on Friday, “had Congress intended to convey the distinct and extraordinary power to impose tariffs.”

Trump has separately slapped sector-specific charges on imports of steel, aluminum, and other items, and the verdict has no bearing on those levies.

There are still a number of government investigations underway that may eventually result in further sectoral levies.

The Supreme Court affirmed lower court rulings that Trump’s IEEPA tariffs were unlawful on Friday, with three liberal justices joining three conservatives.

Clarence Thomas, Samuel Alito, and Brett Kavanaugh, all conservative justices, dissented.

“IEEPA contains no reference to tariffs or duties,” Chief Justice John Roberts stated in his conclusion.

In May, a lower trade court’s decision that Trump had overreached himself with the sweeping duties and barred the majority of them from going into force was halted while the US filed an appeal.