No one on the Supreme Court has gone further to enable Donald Trump’s extreme exercise of presidential power than the chief justice of the United States, John Roberts. Associate justices have also written some important opinions shaping executive power, and the Court has issued ever more important unsigned orders, but the most transformative opinions—the opinions that directly legitimize Trump’s unprecedented uses of power—are Roberts’s handiwork. This is not happenstance. Under Supreme Court practice, the most senior justice in the majority—which is always the chief justice when he so votes—determines who will write the main opinion. Roberts reserved these milestones for himself.

And what milestones they have been. Roberts upheld the first Trump administration’s “Muslim ban” on the grounds that the president’s national-security role precludes courts from taking account of the bigotry undergirding an immigration order. He remanded a lower court’s enforcement of a congressional subpoena for Trump’s financial information, writing that “without limits on its subpoena powers,” Congress could exert “imperious” control over the executive branch and “aggrandize itself at the President’s expense.” He has come close to giving the president an untrammeled right to fire any officer in the executive branch at will. And he took the lead in inventing a presidential immunity from criminal prosecution that could exempt the president from accountability for even the most corrupt exercises of his official functions.

Going beyond the precise holdings in these cases, Roberts’s superfluous rhetoric about the presidency has cast the chief executive in all-but-monarchical terms. The upshot is a view of the Constitution that, in operation, comes uncomfortably close to vindicating Trump’s: “I have an Article II, where I have the right to do whatever I want as president.” Trump’s confidence is surely bolstered also by the Roberts Court’s unsigned per curiam opinions blocking even temporary relief from his sweeping actions. In May, the Court held that Trump orders removing two federal officials at key independent agencies could remain in place while the issue of their legality makes its way through the judiciary. In June, it allowed the administration to proceed with so-called third-country deportations—that is, deporting undocumented noncitizens summarily to countries to which they had no prior connection, but where they might well face torture. On July 8, the Court effectively allowed Trump to proceed with a massive restructuring of the federal executive branch, notwithstanding that the power over executive-branch organization belongs to Congress, not the president. On July 14, the conservative majority allowed the sabotaging of the Department of Education to proceed. Trump’s use of executive power is not a distortion of the Roberts Court’s theory of the presidency; it is the Court’s theory of the presidency, come to life.

What America is witnessing is a remaking of the American presidency into something closer to a dictatorship. Trump is enacting this change and taking advantage of its possibilities, but he is not the inventor of its claim to constitutional legitimacy. That project is the work of John Roberts.