Costco is suing the Trump administration over some of its sweeping tariffs, claiming they're illegal.

In a lawsuit filed Friday, the wholesaler writes it is seeking a "full refund" for duties it has paid to the government due to tariffs imposed under the International Emergency Economic Powers Act

or IEEPA.

That act is a 1977 law that President Trump has used as the basis for many of his tariffs. It gives the president broad power to regulate imports and exports under certain circumstances.

The legality of the president's use of that law to impose tariffs was the focus of a Supreme Court case argued in November in which justices appeared skeptical of the administration's defense of the law.

"It doesn't say 'regulate tariffs,' It says, 'regulate importations and exportations,'" Justice

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