Thursday’s ruling by three judges on the Ninth Circuit Court of Appeals, which upheld a freeze on the Trump Administration's anti-Muslim travel ban, was obviously a significant legal setback for the White House. My colleague Amy Davidson explained how the judges dismissed practically every argument that the Justice Department had presented to them. The ruling’s biggest repercussion for Trump, however, might be a political one. On just his twenty-first day in office, three very senior federal judges, one of them a Republican appointee, issued a stunning smackdown of his divisive and dangerous approach to governing.

When you get down to it, Trumpism is about three things: economic protectionism, American nativism, and creeping authoritarianism. In their ruling, the Ninth Circuit judges took direct aim at both nativism and authoritarianism. They asserted that foreign nationals living in the United States, who could be impacted by the travel ban, are entitled to some of the due-process protections that the U.S. Constitution affords American citizens. And they rejected the Justice Department's argument that some of the President's actions, particularly those driven by national-security concerns, are beyond the review of the courts. “It is beyond question that the federal judiciary retains the authority to adjudicate constitutional challenges to executive action," the ruling said.

Anyone who cares about the future of democracy should be giving thanks this week to the Ninth Circuit’s Judge William C. Canby, Jr., a Jimmy Carter appointee; Judge Richard R. Clifton, whom George W. Bush elevated to the court; and Judge Michelle T. Friedland, who was appointed by Barack Obama. By issuing an unsigned ruling, they emphasized their unity. In going beyond the narrow merits of the case to reassert some general principles about the Constitution and the limits of executive power, they sent a message to the new President, and to the world. Even though Trump controls two branches of the federal government, the third branch—the judiciary—will not bow to his diktat.

The case will now likely go to the Supreme Court—and, as Jeffrey Toobin points out, its fate there is far from certain—but the importance of the message this ruling sent can scarcely be overestimated. In Trump's first weeks in office, every worry about the threat that he poses to American democracy has been justified. He has attacked his political opponents, vilified the media, berated anyone who has questioned him (including federal judges), refused to divest from his businesses, and cozied up to Vladimir Putin. This is someone who clearly aspires to be an American strongman—a President who, if not completely above the law, is more loosely tethered by it than any of his predecessors.

After Election Day, I said that the job of protecting American democracy would fall on "the institutions that claim to embody it, and the people who say they value it." So far, the report card is mixed. Congress, under the control of Trump's Republican allies, has generally done his bidding: confirming his Cabinet nominees, ignoring his flagrant ethics violations, and supporting his executive orders, including the hastily assembled travel ban.

The news media have performed better than Congress. Various outlets are now, at least, calling out Trump and his aides for their constant stream of untruths. And the American people have outdone the press. At the huge Women's Marches, on Inauguration weekend, and then at rallies all across the country against the travel ban, a few weeks ago, large numbers of citizens have stated loudly and clearly that they won't stand by idly as Trump tramples on their notions of America. If nothing else, the sight of so many people taking to the streets has stiffened the resolve of the Democratic leadership in Congress.

So far, though, it is the federal judiciary that has provided the most effective check on Trump. It first took action on the last Saturday in January, a day after the White House imposed the travel ban, when Judge Ann M. Donnelly, of the Federal District Court in Brooklyn, issued an order preventing border agents from deporting people who had been stopped at the airports. Then, last week, Judge James Robart, in Seattle, issued a temporary restraining order that froze the ban nationwide.

Trump fumed publicly about Robart’s decision, and what role his reaction played in the Ninth Circuit decision can only be speculated upon. But the President's ugly dismissal of Robart as a "so-called judge," and his alarming suggestion that, in the event of a future terrorist attack, the judge would have blood on his hands, appalled and infuriated judges everywhere. Among the aggrieved, we now know, was Trump's own nominee to the Supreme Court, Neil Gorsuch. According to the Republican Senator Ben Sasse, Gorsuch told him earlier this week, “Any attack on brothers or sisters of the robe is an attack on all judges.”

Trump, of course, can barely help himself. After the Ninth Circuit ruling was released, on Thursday night, he issued an all-caps broadside on Twitter which read, in part, “SEE YOU IN COURT.” (Presumably, he meant the Supreme Court.) A bit later, he told reporters at the White House that the judgment was "a political decision." On Friday morning, he was back on offense, calling the ruling "a disgraceful decision!"

By Friday afternoon, his tone had changed a bit. In a press conference with the Prime Minister of Japan, Trump seemed to hint that the White House would issue a revised executive order next week. But he also reiterated that he was confident of winning the arguments on the Robart ruling. On cable news, the talking heads were speculating about whether Trump was reassessing his blunderbuss approach.

Let's not kid ourselves. Perhaps, in this instance, some of Trump's political advisers will manage to calm him down. Even if that happens, though, his browbeating approach to the Presidency won't change: it's who he is. In many, many areas, he will need to be opposed, restrained, and hemmed in.

So three cheers for the judges. But this is only the beginning.