As the Supreme Court heard oral arguments today about birthright citizenship, Donald Trump was watching from the courtroom—an apparent first for a sitting president. He listened silently as the justices pelted skeptical questions at Solicitor General John Sauer, who tried to defend a Trump executive order purporting to deny citizenship to the U.S.-born children of certain immigrants. Not long into arguments by Cecillia Wang, the ACLU lawyer representing Trump’s challengers, the president got up and left. The odd scene reflected the administration’s approach to the matter of birthright citizenship: Simply declare you are right, and then ignore arguments to the contrary. Yet if Trump intended his presence to pressure the justices into siding with him, he failed. Most of the justices, even among the conservative supermajority, seemed inclined to strike down his policy. Still, the fact that this case got as far as it did—and that the justices had to consider it seriously enough to spend their time rebuking it—is itself a scandal. The case, Trump v. Barbara, turns on the Trump administration’s argument that …