A protester with the Main Street Alliance displayed a sign outside the U.S. Supreme Court as the justices prepared to consider President Donald Trump's attempt to sustain significant tariffs. Earlier courts had determined that Trump exceeded his authority. This took place in Washington, D.C., on November 5, 2025.
Following the hearing, the likelihood of the Supreme Court ruling in support of Trump's tariffs dropped significantly on platforms like Kalshi, going from nearly 50% to about 30%.
Traders adjusted downward their predictions regarding the court's support for Trump's assertive tariff measures after justices expressed skepticism on Wednesday about the legality of the administration's extensive trade powers.
A similar trend was observed on Polymarket, where related contracts fell to around 30% from over 40% earlier in the week. This indicates an increased belief among traders that the justices might overturn the tariffs.
The shift in market sentiment followed comments from several conservative justices who, along with their liberal counterparts, voiced concerns over the broad authority Trump claimed under the International Emergency Economic Powers Act to enforce tariffs on imports. They rigorously questioned Solicitor General D. John Sauer about the legal rationale backing the tariffs, which opponents argue encroach on Congress's power to levy taxes.
Federal courts have previously ruled that Trump did not possess the necessary legal authority to enact the reciprocal tariffs on imports from numerous U.S. trading partners, as well as fentanyl tariffs on products from countries like Canada, China, and Mexico.
Prediction markets, known for allowing traders to speculate on the outcome of real-world events, quickly reflect perceived judicial inclinations in high-profile cases. Wednesday's change suggested that traders interpreted the justices' remarks as unfavorable for the president's trade policy.
The Supreme Court will not announce its decision on the case immediately. The timeline for the court's ruling remains uncertain.