A Main Street Alliance participant holds a sign outside the U.S. Supreme Court as oral arguments are scheduled for President Donald Trump’s proposal to maintain significant tariffs after a lower court ruled that the president overstepped his authority, November 5, 2025, in Washington, DC.
Nathan Howard | Reuters
Traders lowered the chances of the Supreme Court upholding President Donald Trump’s strong tariffs after the justices on Wednesday suggested doubts about the legality of the administration’s sweeping trade powers.
As for Carsi, the deal, which hinges on whether the court rules in favor of President Trump’s tariffs, has fallen to about 30% from nearly 50% before Wednesday’s hearing.
Similar execution rates on platform Polymarket fell to around 30% from more than 40% earlier in the week, reflecting traders’ growing belief that a judge could invalidate the policy.
The move comes after several liberal justices joined liberal justices in expressing concerns about President Trump’s broad authority to impose tariffs on imports under the International Emergency Economic Powers Act. They grilled Attorney General D. John Sauer on the legal legitimacy of the Trump administration’s tariffs, which critics say violate Congress’ taxing authority.
A lower federal court ruled that President Trump did not have the legal authority to impose so-called reciprocal tariffs on imports from many of the United States’ trading partners, and to impose fentanyl duties on products from Canada, China and Mexico.
Prediction markets, which allow traders to bet on real-world events, often react quickly to signals perceived during high-profile court hearings. Wednesday’s changes suggest traders view the justice’s tone as an indicator of headwinds to the president’s trade policy.
The Supreme Court is not expected to rule on the case Wednesday. It is not clear when the court will announce its decision.
