The rally was led by tech firms, which have been at the forefront of regional gains this year as traders turn away from Wall Street to seek out cheaper investments amid concerns about extended valuations.
Trump’s trade agenda was dealt a hefty blow Friday when the country’s top court ruled that the International Emergency Economic Powers Act (IEEPA) used by the White House to impose sweeping levies in April “does not authorise the president to impose tariffs”.
A furious president immediately vowed to impose a global tariff of 10% under a separate authority, before raising it to 15% on Saturday.
However, the measures have numerous carve-outs and are only legally allowed to remain in place for 150 days.
The development fanned a fresh round of uncertainty, with calls growing for the government to repay cash taken under the scheme and analysts warning officials would likely pursue other ways of imposing his tolls.
“The first observation to make is that IEEPA tariffs may be dead, but Trump’s trade regime isn’t,” wrote Rodrigo Catril at National Australia Bank.
“The administration has several avenues it can pursue, these are likely to be litigated over several years, but there is no sign President Trump is planning to back down.
“Another conclusion is that the tariff landscape is now more uncertain than before, uncertainty is not good news for any economy or market.
“Unless commonsense prevails, we could be entering a circular process where new tariffs are announced, then potentially overturned, only for new tariffs to be announced, and we do the dance again,” Catril said.
The decision also raised questions about trade deals Washington has signed.
European leaders had been due to approve the EU-US deal on Tuesday but the head of the European Parliament’s trade committee said he would call Monday for putting “legislative work on hold until we have a proper legal assessment and clear commitments from the US side”.
Bloomberg reported that Indian trade officials will postpone a trip to the US aimed at finalising their interim agreement.
China said today it was conducting a “comprehensive assessment” of the ruling’s impact, and called on Washington to lift the tariffs.
“China urges the US to cancel its unilateral tariff measures on its trading partners,” the ministry said in a statement.
“There are no winners in a trade war and that protectionism leads nowhere,” it added.
Asian investors welcomed the Supreme Court’s decision, which is seen as benefiting China and India, with tech firms the best performers.
Hong Kong rose more than 2%, with e-commerce titans Alibaba and JD.com surging more than 3%, while Seoul hit another record high thanks to big advances for chipmakers Samsung Electronics and SK hynix.
Singapore, Wellington, Taipei, Mumbai, Bangkok and Manila also rose, though Sydney dipped. Tokyo and Shanghai were closed for holidays.
“This looks less like ‘tariffs are over’ and more like ‘effective tariffs may be lower than feared, but policy uncertainty and fiscal noise remain high’,” wrote Saxo Markets chief investment strategist Charu Chanana.
The strong start to the week followed gains on Wall Street, where the tariff ruling overshadowed data showing the US economy grew much slower than expected in the fourth quarter of 2025, when it was hit by the extended government shutdown.
The uncertainty also weighed on the dollar, which was well down against the yen, pound and euro.
Oil prices dropped around 1% amid hopes for an Iran nuclear deal.
That has tempered last week’s concerns about a possible US strike on the country after Trump warned “bad things happen”, as he deployed warships, fighter jets and other military hardware to the Middle East.