U.S. politics is apt to conflate disagreements about whether a policy is good or bad with disputes about whether it is constitutional. Reactions to the Supreme Court’s ruling on President Donald Trump’s tariffs are a good example. Most commentators seem drawn to one of two positions: The tariffs are either bad policy and an abuse of presidential power, or good policy and constitutionally proper. Yet the criteria in question have little to do with each other. I think Trump’s tariffs are foolish — a reckless repudiation of tried-and tested economics that jeopardizes America’s stunning economic strengths. But set that aside. Why exactly is this policy, smart or stupid as the case may be, illegal? The court has ruled against the bulk of Trump’s tariffs on what seems a narrow technicality. According to the majority’s ruling, the statute purportedly authorizing the administration’s signature policy — the International Emergency Economic Powers Act — lets the White House “regulate” trade under certain circumstances but precludes tariffs as a way to carry out that regula