President Trump says his administration should win a major legal case against his tariff authority on legal grounds and on “common-sense” merits, warning the U.S. would have to refund “trillions” if he loses.

The Supreme Court agreed to speed the case to its calendar, scheduling oral argument for the first week of November. 

Mr. Trump is warning of economic devastation if he loses to blue states and small businesses, who say he overstepped by using a 1977 law to slap levies on dozens of trading partners.

“We would have to give back trillions and trillions of dollars,” Mr. Trump said Friday on “Fox & Friends.” “We’re a rich, powerful country, and when we’re rich, we can do more things for the people.”

Treasury Scott Bessent estimates the U.S. would have to repay $750 billion to $1 trillion if the administration loses the case and the opinion doesn’t arrive until June.

The case hinges on whether Mr. Trump lawfully invoked the International Emergency Economic Powers Act to impose his tariffs. 

The law gives the president certain powers over international commerce. However, a trade court and an appeals court, in ruling against Mr. Trump, noted the law doesn’t even mention tariffs.

Mr. Bessent has suggested there are contingency measures the administration could take to keep the tariffs in place, while Commerce Secretary Howard Lutnick told “The Axios Show” it would be “silly” to worry about a loss before the court.

“I don’t want to talk about it. I guess we’ll find something,” Mr. Trump said in his Fox interview. “That case is really important to win.”

Tariffs are a tax on foreign goods brought into U.S. markets. The president recently imposed tariffs ranging between 15% and 41% on more than 67 countries, raising levies to their highest levels in over a century. He’s solidified the 10% blanket tariff on all imports and is implementing the 15% rate he negotiated with places like the European Union, Japan and South Korea.

The case before the Supreme Court would impact those tariffs, plus drug trafficking-related tariffs he slapped on goods from Canada, Mexico and China. It would not impact sector-specific tariffs on steel, aluminum and cars, which did not rely on the IEEPA law.

Mr. Trump, in the Fox interview, said the case was brought by foreign entities, though that is not accurate. The plaintiffs are blue states and small U.S. businesses that rely on imports and claim the tariffs are a hardship.

Overall, Mr. Trump said the economy is doing well, pointing to high stock market numbers and large investments in U.S. manufacturing by foreign companies. He wants the Federal Reserve to jumpstart the economy by slashing interest rates in the coming days. 

Fed Chair Jerome Powell has resisted calls from Mr. Trump to slash interest rates, citing the fear of price inflation due to the White House tariff plan, but a rate cut is all but assured as the U.S. sees a marked slowdown in hiring.

“He’s a year late,” Mr. Trump said of Mr. Powell.

• Tom Howell Jr. can be reached at thowell@washingtontimes.com.