The U.S. Supreme Court's decision to strike down a large swath of President Donald Trump's tariffs has weakened his ability to threaten and impose tariffs at a moment's notice, but it won't end gnawing uncertainty for trade partners or companies. Trump responded within hours to the ruling on Friday, slapping a new 10% tariff on all imports and ordering new trade investigations that could lead to additional levies in months, while insisting that trade and investment deals reached with nearly 20 countries - most with higher tariffs - should remain untouched. Less than 24 hours later, he raised the rate of the new tariff to 15% - the maximum level allowed under the law.