A protester affiliated with the Main Street Alliance held a sign outside the U.S. Supreme Court as its justices prepared to hear oral arguments regarding President Donald Trump’s attempt to maintain extensive tariffs. This follows lower court rulings that Trump had exceeded his authority. The hearing took place in Washington, D.C., on November 5, 2025.
On the prediction market platform Kalshi, contracts predicting that the court would support Trump's tariffs fell to around 30% from nearly 50% ahead of Wednesday's hearing.
Traders lowered the odds of the Supreme Court upholding President Trump's aggressive tariff measures after justices conveyed concerns about the administration's trade powers during Wednesday's session.
Similarly, a corresponding contract on the Polymarket platform dropped to about 30% from over 40% earlier in the week, indicating that traders increasingly believe the justices might overturn the policy.
This shift occurred after several conservative justices joined their liberal peers in expressing discomfort with the extensive authority Trump asserted under the International Emergency Economic Powers Act to enact tariffs on imports. The justices critically examined Solicitor General D. John Sauer about the legal rationale for the tariffs, which detractors argue infringe on Congress's taxation powers.
Lower federal courts have concluded that Trump exceeded his legal authority to apply the so-called reciprocal tariffs on imports from various U.S. trading partners, including the fentanyl tariffs on goods from Canada, China, and Mexico.
Prediction markets, which enable traders to wager on real-world outcomes, tend to react rapidly to perceived shifts during significant court hearings. Wednesday's developments suggested that traders interpreted the justices' inquiries as a sign of potential challenges for Trump's trade agenda.
The Supreme Court is not expected to issue a decision in the case immediately following the hearing. The exact timing of the court's ruling remains uncertain.