As the clock ticks down to President Donald Trump's Aug. 1 deadline for the resumption of reciprocal tariffs, a federal appeals court is hearing arguments Thursday over whether Trump's sweeping tariffs are lawful.

The U.S. Constitution gives the power to impose taxes — including tariffs — to Congress. But lawmakers have gradually relinquished power over trade policy to the White House. And Trump has made the most of the power vacuum, raising the average U.S. tariff to more than 18%, highest since 1934, according to the Budget Lab at Yale University.