In the war of words between President Trump and Chief Justice Roberts, The New York Sun is on the side of the President. We understand the cataract of sanctimony that is going to cascade from the political and journalistic (and actual) pulpits in the wake of Mr. Trump’s remarks in respect of the Notorious Ninth Circuit. That only puts the President’s point into sharper relief.

This feud started when a United States district judge in California sought to block Mr. Trump’s plans to deal with a caravan of potential asylum seekers heading towards the United States. Not to be misunderstood here, the Sun favors a capacious asylum program in the spirit of the New Colossus. If Mr. Trump can sustain the jobs and growth boom in America, we’ll need more immigrants.

Yet the President, who has his own responsibilities in the current conflict, sees the caravan as portending an invasion. That puts him in a position where the Constitution would remove his discretion, giving him not just the power but also the obligation to act, whether he wants to or not. That’s because of Article 4, Section 4, which commands the United States to protect each state against invasion.

Just to mark the point. The Constitution grants to the government the power to do certain things if it wants to. It denies the government the power to do certain other things, even if it wants to. What it does in Article 4, Section 4 is lay on the government the obligation to do certain other things, whether it wants to or not. These are sometimes called the obligation clauses, binding all three branches.

Protecting against invasions, again, is one of the obligations. Besides, it was Judge Tigar who, with his injunction against the president, drew first constitutional blood. Mr. Trump promptly dismissed him as an “Obama judge.” No doubt the country is split as to whether that is a compliment or an insult. All the more startling that Chief Justice Roberts piped up with a statement.

The Chief Justice insisted that America doesn’t have “Obama judges or Trump judges, Bush judges or Clinton judges.” What we have, he added, “is an extraordinary group of dedicated judges doing their level best to do equal right to those appearing before them.” It’s a fair enough point, though these days even the New York Times identifies judges by the president who appointed them.

More broadly, the idea that United States judges are above criticism is a decidedly un-American conceit. Not un-American in the sense that our noble anti-communists used the word. Rather, un-American in that the prohibition on criticizing judges and courts has its roots in an England from which we declared our independence long ago. For good measure, we threw in the First Amendment.

The pecksniffs at the Brennan Center have published a guide on how to criticize a judge. It considers, say, President Obama’s denunciation of the Supreme Court’s justices to their faces for taking, in Citizens United, a broad view of the First Amendment. That happened at a State of the Union address. It was, the Brennan Center’s writer suggests, unusual less for its vitriol than its venue, where the Democratic caucus whooped and hollered.

That horrified us, by the way. In the current feud, though, Mr. Trump gave no quarter. “Justice Roberts can say what he wants,” the President twittered, “but the 9th Circuit is a complete & total disaster.” The 9th Circuit, Mr. Trump pointed out on Twitter, boasts the highest reversal rate in the country. The sweet irony is that Chief Justice Roberts had something to do with making the President’s point.