Trump’s sudden decision to hike his new tariff rate to 15% is ‘something of an eff you’ to the U.K.

The abrupt change followed the Supreme Court’s ruling Friday that struck down his tariffs under the International Emergency Economic Powers Act. Hours after the decision, he imposed a 10% rate under Section 122 of the 1974 Trade Act, then hiked the new duty on Saturday morning.

While experts have pointed out the Section 122 tariffs are also legally dubious, it could take months to sort through any court challenge. And the new rate can only be in effect for up to five months.

But unlike Trump’s attempt to invoke the IEEPA levies, the new ones must be applied uniformly across all trading partners, meaning everyone must face a 15% rate.

That conflicts with the Trump administration’s trade deal reached last year that set a 10% rate on imports from the U.K.

British Prime Minister Keir Starmer notably took a more conciliatory approach to Trump’s stunning “Liberation Day” tariffs last year, and Trump administration officials held up the U.K. trade deal as an example of how playing ball with the U.S. could result in a more favorable rate.

Meanwhile, other top U.S. trade partners like the European Union and Japan reached separate deals that came later, setting 15% rates.

Paul Ashworth, chief North America economist at Capital Economics, speculated that Trump’s abrupt decision to increase his brand new tariff may have been because 10% would have generated less revenue.

“It also means some of America’s biggest trading partners, like the EU and Japan, will find themselves exactly back where they were last week,” he said in a note Saturday. “For the UK that thought it had secured a more advantageous 10% rate, however, this is something of an eff you. From Trump’s perspective though, it was unavoidable since Section 122 explicitly notes that any tariff must be applied in a non-discriminatory manner.”

Ashworth also pointed out that many of the imports that were exempted from the IEEPA tariffs will also be similarly exempted under the new ones.

That means that despite the 5-point hike in the headline rate, the effective tariff rate will rise 2 points from about 12.5% on Friday to 14.5% now, putting it slightly above where it had been before the Supreme Court decision.

The new tariffs won’t stop there either. On Friday, Trump said the administration would also initiate investigations under Section 301 of the 1974 law, which is meant to combat unfair trade practices or violations of trade agreements. Those tariffs can’t be enacted until the investigations are complete, which could take two to three months under an expedited process.

He is expected to use the temporary authority under Section 122 to buy time before the Section 301 investigations can be completed. At the same time, the administration has about a dozen investigations under Section 232 of the 1962 Trade Expansion Act that could lead to more tariffs on national security grounds.

“Needless to say, trade uncertainty in the coming months will remain elevated,” analysts at JPMorgan said in a note late Friday. “Our base case remains that the average tariff rate will settle around the current rate of 9-10%, but the path forward will be fraught with considerable uncertainties. We expect most of the eventual tariffs to be those under Sections 301 and 232. Importantly, the country- and product-specific impact of Section 301 and 232 tariffs could be vastly different from those under the IEEPA tariffs.”