The arguments underscored the financial stakes for U.S. importers as the Trump administration prepares to impose higher rates without the explicit approval of Congress.

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.

Companies, consumers and foreign countries have been paying close attention to President Donald Trump’s aggressive policy of placing tariffs on foreign goods. Soon, the courts will weigh in on whether Trump has the power to levy those tariffs in the first place — a high-stakes legal battle that will either affirm a key pillar of Trump’s economic policy or cut it off at the knees.

The US is seeing increased tariffs income, but there are signs of some countries diverting trade from America.