Today, the Supreme Court is hearing oral arguments in one of those rare cases that could reshape all three branches of government. The justices deciding Learning Resources, Inc. v. Trump, a challenge to the current tariff regime, could determine whether the imperial presidency is entrenched or arrested. They could either cajole Congress out of its dormancy or render it even more inert. And they could buttress the legitimacy of the Court’s conservative majority—which in the past decade has aggressively intervened to limit the administrative state’s domestic operations—or undermine it by applying different standards to presidents of different parties.

The Court will consider whether Donald Trump’s tariffs, which have roiled global markets and rankled America’s allies, are unconstitutional because the president imposed them unilaterally. After decades of near-zero duties, America now has an overall tariff rate of about 17 percent—the highest since 1935. This has come about through presidential decree alone, with no congressional input whatsoever. Under Chief Justice John Roberts, the Court has become more indulgent toward the president’s power over foreign affairs and within the executive branch itself (in keeping with the so-called unitary-executive theory). But taxation and the imposition of tariffs are core powers of Congress, explicitly assigned to it by the Constitution. Crediting the president’s powers here would be an aberration from the Court’s own recent precedents.

The Trump administration argues that it can set tariffs however it likes by relying on a maximalist reading of the International Emergency Economic Powers Act, or IEEPA.