By Mike Scarcella

WASHINGTON, March 11 (Reuters) - Costco Wholesale COST.O was sued on Wednesday in a proposed nationwide class action seeking U.S. customer refunds for higher prices charged by the company before the U.S. Supreme Court struck down import tariffs imposed by President Donald Trump.

The lawsuit, filed by a Costco shopper in federal court in Illinois, seeks a declaration that the company must return to customers any refunds it receives for tariffs it paid under the International Emergency Economic Powers Act (IEEPA).

The Supreme Court ruled on February 20 that Trump overstepped his authority by using the emergency powers law to impose sweeping tariffs last year. The order has teed up sprawling litigation in the U.S. Court of International Trade, where Costco is among more than 2,000 companies suing the administration to recover duties they paid.

Global shipper FedEx FDX.N is facing a similar consumer class action filed in Florida federal court last month.

Costco did not immediately respond to a request for comment. A lawyer for plaintiff Matthew Stockov also did not immediately respond to a request for comment.

“This lawsuit seeks to prevent Costco, the third-largest retailer in the world, from double recovery,” the complaint said. “Costco has made no commitment to return any portion of anticipated tariff refunds to the consumers who bore those costs.”

Costco CEO Ron Vachris told analysts last week that it was still unclear if or when businesses will get back the IEEPA tariffs they previously paid. If Costco does receive refunds, he said, the retailer plans to channel them into lower prices and improved value for shoppers.

Wednesday's lawsuit said the company was promising only "a possible future benefit to an indeterminate group of future shoppers."

(Reporting by Mike Scarcella; Editing by David Bario and Aurora Ellis)

((Email: mike.scarcella@thomsonreuters.com; Phone: 202-985-8228.))