A protester with the Main Street Alliance stood outside the U.S. Supreme Court as the justices prepared to hear oral arguments on President Donald Trump's attempt to maintain expansive tariffs, which had been deemed overreaches of authority by lower courts, in Washington, D.C., on November 5, 2025.
On the prediction market platform Kalshi, the probability that the court would back Trump's tariffs dropped to around 30% from nearly 50% prior to Wednesday’s hearing.
Traders reduced their expectations that the Supreme Court would uphold Trump's aggressive tariffs after justices conveyed doubts about the legality of the administration’s substantial trade powers during Wednesday's session.
Similarly, a contract on Polymarket fell to about 30% from over 40% earlier in the week, indicating traders increasingly doubt the policy will survive judicial scrutiny.
The shift in betting odds followed remarks from several conservative justices who, together with their liberal counterparts, expressed concern over the extensive authority Trump claimed under the International Emergency Economic Powers Act to impose import tariffs. They rigorously questioned Solicitor General D. John Sauer regarding the administration's legal rationale for the tariffs, which critics argue overstep Congress's taxation powers.
Lower federal courts have already ruled that Trump lacked the authority to enforce the so-called reciprocal tariffs on imports from numerous U.S. trading partners, as well as fentanyl tariffs on products from Canada, China, and Mexico.
Prediction markets, which enable traders to place bets on real-world events, often react swiftly to signals perceived during significant court hearings. Wednesday's market movements suggest traders interpreted the justices' tone as a potential obstacle to the president's trade policies.
The Supreme Court is not expected to issue a decision in the case immediately. The timing of the court's ruling remains uncertain.