The odds that the Supreme Court will uphold President Donald Trump’s tariffs collapsed to as low as 18% during Wednesday’s oral arguments, reflecting broad skepticism from the justices about whether emergency powers law authorizes sweeping import taxes.
The court convened to test whether the International Emergency Economic Powers Act permits the White House to impose global tariffs in the name of national emergencies. Chief Justice John Roberts immediately framed tariffs as taxes, historically a core congressional power, and several conservative and liberal justices pressed the government on statutory limits.
A related prediction market that pays out only if the Supreme Court reverses or vacates the Federal Circuit’s August decision against the tariffs saw odds hit an intraday trough near 18%, then recover into the high-20s to low-30s range by late afternoon.
BREAKING: The odds of President Trump's tariffs being ruled as "legal" by the Supreme Court collapse to just 18%, per Polymarket. https://t.co/ZQXBeSmoXc pic.twitter.com/cImHmzHT55
— The Kobeissi Letter (@KobeissiLetter) November 5, 2025
On substance, justices questioned whether IEEPA’s authority to “regulate importation” reaches tariff imposition without a clear congressional grant, and several invoked the major-questions doctrine as a potential constraint.
Lower courts have already found the IEEPA-based tariffs unlawful, prompting Wednesday’s appeal. The government noted that IEEPA collections reached an estimated $89 billion through late September and argued the measures are a foreign-affairs tool, not a revenue program, while challengers countered that such breadth requires explicit congressional approval.
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