The majority of the sweeping tariffs Donald Trump imposed during his second term face one final litmus test that will determine whether he can continue to levy them – and also whether businesses are eligible for massive refunds.

That potentially dramatic turn in the tariff saga comes after a federal appeals court ruled on Friday that Trump unlawfully leaned on the International Emergency Economic Powers Act (IEEPA) to impose across-the-board duties on countries.

Trump had used those powers to push import tax rates as high as 50% on India and Brazil – and as high as 145% on China earlier this year.