The Treasury secretary’s criticism comes after he attended arguments over President Trump’s tariff authority last year.

US Trade Representative Jamieson Greer said new levies would begin “the next day” if the court rules against the White House. India is among the worst-hit countries, facing 50% tariffs.

If the court rules that the president does not have "emergency" powers to regulate routine international trade then his latest threats on Greenland would become technically meaningless.

Gableman, a former justice of the Wisconsin Supreme Court, argues that the process itself is unconstitutional. He claims that three of the liberal justices' refusal to recuse themselves from matters connected to his case violates his 14th Amendment right to due process.

If the Supreme Court rules against its tariffs, the Trump administration would begin replacing them immediately, said Jamieson Greer, the United States Trade Representative.