WASHINGTON - Donald Trump's key tool for deploying tariffs faced tough questions from the conservative-led U.S. Supreme Court on Wednesday as justices considered a decision that could upend the president's plans to rapidly realign global trade.

Neal Katyal, the attorney representing businesses pushing back on Trump's tariffs, told the hearing that Trump has "torn up the entire tariff architecture."

"That is not something the president has the power to do," Katyal said.

Trump used the International Emergency Economic Powers Act of 1977, known as IEEPA, for his "Liberation Day" tariffs and fentanyl-related duties on Canada, Mexico and China.

During the nearly three-hour hearing, the Supreme Court justices parsed the language in IEEPA, particularly the wording about the president's "power

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