Justice Ketanji Brown Jackson’s criticisms of “relentless attacks on judges” that are “undermining our Constitution and the rule of law” could be heard as a battle cry from the judicial left — and a sign that liberals in the judiciary may be taking the gloves off for an all-out brawl with President Trump.

The looming question is whether protestations like those of Justice Jackson are just howls at the moon, or whether moderate and conservative judges will join her in pushing back against Mr. Trump’s brute exertions of executive power. 

Justice Jackson, the most junior member of the Supreme Court, speaking at a conference for judges at Puerto Rico, ruminated: “ Across the nation, judges are facing increased threats of not only physical violence, but also professional retaliation just for doing our jobs … the attacks are not random. They seem designed to intimidate those of us who serve in this critical capacity.” Justice Jackson called the hostility to judges the “elephant in the room,” and did not name Mr. Trump.  

The 47th president has long eschewed restraint in his criticism of lower-level federal judges who’ve blocked — at least temporarily — his policies. Most recently, he called Judge James Boasberg, who’s pushed back at Mr. Trump’s use of the 1798 Alien Enemies Act against alleged gang members, a “Radical Left Lunatic, a troublemaker and agitator.”

That outburst — and the ensuing endorsement of impeachment articles against Judge Boasberg — was so caustic that it prompted a response not from one of the court’s liberal lions like Justice Jackson, but from Chief Justice Roberts. He wrote in a statement: “For more than two centuries … it has been established that impeachment is not an appropriate response to disagreement concerning a judicial decision. The normal appellate review process exists for that purpose.”

The Supreme Court moved the case to Texas from Judge Boasberg’s courtroom at the District of Columbia, but he still retains control over some of the ancillary proceedings, including one where he has already found “probable cause” that the Trump administration met the bar for criminal contempt when it “deliberately flouted” his orders to turn back, in mid-air, two planes full of Venezuelan migrants — who America claims are members of the Tren de Aragua gang — bound for El Salvador.     

The Trump administration is particularly exercised by the ability of a single district court judge to block an action of national consequence by the commander in chief, even when the action involves foreign policy. At a Cabinet meeting earlier this week, Secretary Rubio was pointed in his criticisms of judges who get involved in immigration policy, which he said was the sole prerogative of the president.

Mr. Trump has, even as he’s railed against liberal judges, repeatedly said he will abide by the courts, a pledge repeated by Attorney General Bondi, and the Trump administration has indeed largely abided, perhaps with the exception of not turning around those El Salvador-bound planes.

Chief Justice Roberts’s defense of Judge Boasberg, an appointee of President Obama, was not the first time he has pushed back against comments from Mr. Trump. In 2018, after the then-45th president castigated what he called an “Obama judge,” the Chief wrote: “We do not have Obama judges or Trump judges, Bush judges or Clinton judges. What we have is an extraordinary group of dedicated judges doing their level best.”

There could be signals that the high court, despite its conservative majority, is translating some of its pushback against Mr. Trump into its opinions. Last month the Nine issued an unusual order on a Saturday night, a temporary ruling that blocked the Trump administration from deporting a group of immigrants in Texas under the Alien Enemies Act. 

On its face, the court merely tabled a decision on the deportations until it could be heard in court. But that the decision opened up fault lines among the justices could be discerned from a dissent issued by Justice Samuel Alito, who castigated his colleagues for weighing in “literally in the middle of the night” and issuing “unprecedented and legally questionable relief without giving the lower courts a chance to rule” and without “hearing from the opposing party.” 

Justice Clarence Thomas also dissented. That suggests, though, that the rest of the court’s conservatives — Justices Roberts, Amy Coney Barrett, Brett Kavanaugh, and Neil Gorsuch — voted for the freeze.

Resistance to Mr. Trump’s posture toward the courts also appears to be rising among conservative lower court judges. One of the leading lights of the appellate bench, Judge Harvie Wilkinson of the Fourth United States Appeals Circuit, issued a scathing opinion against the administration’s behavior in the case involving the deportation of alleged gang member Kilmar Abrego Garcia, whom the Trump administration says belongs to MS-13.

The circuit rider warned that the judiciary and the executive were “too close to grinding irrevocably against one another in a conflict that promises to diminish both.” Judge Wilkinson, who was named to the bench by President Reagan, accused Mr. Trump of “asserting a right to stash away residents of this country in foreign prisons without the semblance of due process that is the foundation of our constitutional order.”

If Justice Jackson’s broadside conveyed sentiments that are shared even by her conservative colleagues, Mr. Trump’s signature initiatives could be in trouble as the Supreme Court barrels toward its busiest time of the year. On its calendar for oral arguments are, say, cases that turn on Mr. Trump’s efforts to end birthright citizenship and terminate the use of nationwide injunctions by district court judges.

On Thursday a judge appointed by Mr. Trump, Fernando Rodriguez Jr. of the Southern District of Texas, permanently banned, in his jurisdiction, use of the Alien Enemies Act to deport Venezuelans to El Salvador. Judge Rodriguez Jr. found that Mr. Trump’s use of the law “exceeds the scope of the statute and is contrary to the plain, ordinary meaning of the statute’s terms.” That ruling, too, appears ticketed for the high court.