The Supreme Court‘s Wednesday oral arguments over the legality of Donald Trump‘s sweeping “Liberation Day” tariffs pitted the president’s constitutional foreign affairs powers against Congress’s constitutionally delegated tariff power.

The justices appeared highly skeptical of Solicitor General D. John Sauer’s arguments that the president’s sweeping tariffs under the International Emergency Economic Powers Act are lawful. Chief Justice John Roberts questioned how Sauer’s claim that the president’s broad leeway in foreign affairs squares with Congress’s explicit power to tax and tariff, as outlined in the Constitution.