WASHINGTON — Costco is joining other companies that aren’t waiting to see whether the Supreme Court strikes down President Donald Trump’s most sweeping import taxes. They’re going to court to demand refunds on the tariffs they’ve paid.

The specialized U.S. Court of International Trade in New York and the U.S. Court of Appeals for the Federal Circuit in Washington ruled earlier this year that Trump’s biggest and boldest import taxes are illegal. The case is now before the Supreme Court. In a Nov. 5 hearing, several of the high court’s justices expressed doubts that the president had sweeping power to declare national emergencies to slap tariffs on goods from almost every country on Earth.

If the court strikes down the tariffs, importers may be entitled to refunds on the levies they’ve paid. “It’s uncertain whether refunds will be granted and, if so, how much,” said Brent Skorup, a legal fellow at the libertarian Cato Institute. ”But the possibility has prompted many companies — including Costco — to file actions in the U.S. Court of International Trade to get in line, so to speak, for potential refunds.”

Trump claims that he has an almost unlimited right to impose tariffs — a power the Constitution gives to Congress, under the 1977 International Emergency Economic Powers Act (IEEPA) — but has now lost twice in court. Trade lawyer Joyce Adetutu, a partner at the Vinson & Elkins law firm, said that Costco is trying to “make sure that if and when the Supreme Court overturns the IEEPA tariffs, which could come as late as the summertime, they have the judgment in place’’ and can collect a refund.

In a complaint filed last week with the trade court in New York, Costco said it is demanding the money back now “to ensure that its right to a complete refund is not jeopardized.″

The operator of warehouse-sized stores expressed concern that it might struggle to get a refund once its tariff bills have been finalized — a process called “liquidation” — by the Customs and Border Protection agency, a process Costco says will start Dec. 15. Importers have 180 days after liquidation to protest the tariff bills. Costco worries that “their timeline might be whittled away depending on how long it takes to get a Supreme Court decision,” Adetutu said.

Revlon and canned seafood and chicken producer Bumble Bee Foods have made similar arguments in the trade court.

The tariffs facing the court challenge have raised around $90 billion so far.

It’s unclear how a refund process would work. As import tax bills are finalized and sometimes appealed, Customs and Border Protection “refunds tariffs every day, but not to this extent,” Adetutu said. “This is a substantial amount of tariff income that has been collected. And really there hasn’t been a case where there’s been an influx of refund requests.’’

Trump warned back in August that the loss of his tariffs would destroy that American economy and lead to “1929 all over again, a GREAT DEPRESSION!”