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”.
And Bloomberg reported that Indian trade officials will postpone a trip to the United States aimed at finalising their interim agreement.
China said Monday it was conducting a “comprehensive assessment” of the ruling’s impact, and called on Washington to lift the tariffs.
“China urges the United States to cancel its unilateral tariff measures on its trading partners,” the ministry said in a statement. “There are no winners in a trade war … protectionism leads nowhere.”
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 per cent, with e-commerce titans Alibaba and JD.com surging more than 3 per cent, 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.
London, Paris and Frankfurt all dropped at the open.
“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.
And oil prices dropped more than one percent 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.