Global trade flows were thrown into fresh uncertainty after the Supreme Court of the United States invalidated President Donald Trump’s “reciprocal” tariff framework, forcing governments and businesses to reassess the rules governing U.S. imports.

In place of the struck-down system, a flat 10% global tariff on U.S. importers took effect Tuesday. The rate is lower than the 15% level Trump had signaled days earlier. The administration is relying on Section 122 of the Trade Act of 1974, which allows such a tariff to remain in effect for up to 150 days without congressional approval.

Economists say the ruling significantly reshapes competitive dynamics, particularly for China. Alicia García-Herrero, chief economist for Asia-Pacific at Natixis, described Beijing as the “biggest winner,” noting that the effective U.S. tariff rate on Chinese goods is now much closer to that imposed on other trading partners.

A narrower tariff gap reduces the incentive for multinational firms to relocate manufacturing from China to other Asian economies — at least in the short term — potentially stabilizing supply chains that had been shifting in response to higher U.S. duties.

At the same time, the abrupt policy reversal has introduced new uncertainty for key U.S. allies and major trading partners. Several countries had either finalized or were close to securing bilateral trade arrangements with Washington under the now-invalidated tariff regime, in some cases offering substantial concessions to lock in preferential rates.

In Asia, administration officials had accelerated negotiations in the weeks leading up to the ruling. Indonesia, for example, agreed just a day earlier to a 19% tariff rate under the previous framework.

The decision also lands at a sensitive diplomatic moment. Trump is scheduled to travel to China in the coming weeks, where he aims to preserve a fragile trade truce with the world’s second-largest economy amid shifting legal and economic terrain.