Last Thursday, on the same day that Trump blitzed the world, yet again, with a new round of tariffs on a broad range of goods, a specialized appeals court in Washington, D.C., inched closer to a definitive pronouncement on whether the President can legally make such sweeping economic demands—on a whim, whenever he feels like it.

Democratic-led states and U.S. businesses challenging tariffs in court argue that IEEPA does not cover tariffs, and that Congress has authority over tariffs and taxes.