Markets waver as court voids tariffs and Trump seeks 15% baseline

The U.S. Supreme Court struck down most of President Donald Trump’s sweeping global tariffs and the White House signaled a baseline import duty of 15%, a policy shock that sent S&P 500 futures down roughly 0.5–0.7% on Monday while Hong Kong’s Hang Seng jumped about 2.2% as investors scrambled to price winners and losers.

Yahoo UK reported the Court’s decision as a 6-3 ruling. President Trump said on Saturday he would raise the baseline tariff rate from 10% to 15% and that the change was “effective immediately,” but Reuters, AP and Yahoo UK all noted it was unclear whether formal administrative steps had been taken to implement the higher duties. On CBS, U.S. Trade Representative Jamieson Greer said the ruling “won’t undo deals negotiated with US partners including the EU, China, Japan and South Korea,” and that those deals are separate from the new 15% tariff, according to Yahoo UK.

Market reactions in Asia were mixed. AP reported the Hang Seng surged 2.2% to 27,003.47 while the Shanghai Composite fell 1.3% to 4,082.07, South Korea’s KOSPI rose 1.1% to 5,873.07 and Taiwan’s Taiex climbed 1.4%; AP noted Tokyo was closed for a holiday. Reuters and regional analysts showed slightly different intraday moves: Reuters said the KOSPI rose about 2.0% and MSCI’s Asia-Pacific ex-Japan index edged up 0.5%, while Moderndiplomacy and FinancePremium cited a 2.53% Hang Seng gain and a 0.83% rise in MSCI Asia ex-Japan. The reporting differences likely reflect timing and data sources; each outlet’s figures are cited with attribution.

U.S. futures reacted with caution. AP put S&P 500 futures down 0.7%, Dow futures down 0.6% and Nasdaq futures down 0.8%. Yahoo UK reported similar moves, Dow futures down 0.6%, S&P futures down 0.7% and Nasdaq 100 futures down about 0.9%, while Reuters noted a somewhat smaller pullback, with S&P futures down 0.5% and Nasdaq futures down 0.6%.

European markets opened modestly lower. Moderndiplomacy reported STOXX 600 down 0.19%, Germany’s DAX down 0.36% and Britain’s FTSE 100 down about 0.1%, while Yahoo UK showed the FTSE off roughly 0.18% as traders sought clarity on tariff implementation.

Currencies and safe havens reflected the unsettled mood. Reuters said the dollar eased about 0.4% against the yen to 154.36 and gained versus the euro and Swiss franc shifted, while CNBC reported the U.S. dollar index slid close to 0.3%, the 10-year Treasury yield lost a little over one basis point and gold inched up about 0.8% on safe-haven demand. Reuters also noted 10-year futures were down slightly and that mixed domestic data had reduced the market’s probability of a June Fed rate cut to around 52% from above 60% a week earlier.

Analysts emphasized policy-driven winners and losers. Benjamin Picton of Rabobank wrote that the moves highlighted “the winners-and-losers effect of shifts in tariff policy that has just delivered a boost to countries who previously had a comparatively bad deal,” adding that “U.S. tariff policy will continue to be a source of uncertainty for markets as traders attempt to price in the implications of what is still a movable feast,” as quoted by AP. Ed Yardeni of Yardeni Research told CNBC that “The market didn’t really react much to the news. It was already widely anticipated.”

The immediate market takeaway is volatility around policy uncertainty rather than a clear directional shock. With the EU reportedly pausing ratification talks pending clarity and questions remaining about which products or countries would face any uniform 15% rate, investors said the next moves to watch are formal White House or U.S. Trade actions and upcoming corporate results, including Nvidia’s earnings this week, which Reuters flagged as a test of sentiment in the AI trade.