According to Yahoo news: Small businesses and several states sued, and lower courts split until the Supreme Court agreed to intervene.

According to AI; several parties: Small businesses. They sued in the United States District Court for the District of Columbia. Multiple states, including Costco.

Key Plaintiffs and Standing: States (NY, IL, etc.): A coalition of 11+ states, led by 👉AG Letitia James, sued, arguing the tariffs were unlawful and harmed state economies. Businesses (V.O.S. Selections et al.): Represented by the Liberty Justice Center, five owner-operated companies argued the tariffs caused severe economic harm, claiming they constituted an unconstitutional delegation of Congress's taxing power. Other Impacted Companies: Hundreds of firms, including importers like Costco and Alcoa, filed suits in the Court of International Trade for refunds. New York State Attorney General (.gov)

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I did a search and this was the the response:

Multiple companies and U.S. states filed legal challenges against President Donald Trump's tariffs, particularly those imposed under the International Emergency Economic Powers Act (IEEPA).

V.O.S. Selections, Inc. v. Trump was a key lawsuit filed on April 14, 2025, by five small businesses—V.O.S. Selections, FishUSA, Genova Pipe, MicroKits LLC, and Terry Precision Cycling—represented by the Liberty Justice Center. They argued the so-called “Liberation Day” tariffs were unconstitutional and not authorized by IEEPA.

Other major companies that filed lawsuits include:

Dole Fresh Fruit Company Costco Wholesale Goodyear Tire & Rubber Company Toyota subsidiaries BYD Prada Staples Tom Ford Distribution J Crew Group Additionally, twelve U.S. states led by Oregon filed a similar challenge in the Court of International Trade, which was consolidated with the V.O.S. Selections case.

Another significant case, Learning Resources, Inc. v. Trump, was also filed by affected businesses challenging the legality of the tariffs under IEEPA