Chief Justice Roberts likens judges to umpires, but in the birthright citizenship dispute playing out in the federal courts, the next big decision could come from a boxing referee — in his spare time, at least. The case is before a district judge in New Hampshire, Joseph LaPlante. He is not only a jurist but a professor of law, at Boston College, which reports that Judge LaPlante “is a boxing referee, licensed to officiate both professional and amateur bouts.” 

Judge LaPlante’s skill in adjudicating the sweet science will likely come in handy in the sparring between President Trump and the American Civil Liberties Union. A hearing in the birthright case is set for Thursday. Mr. Trump ended the automatic granting of citizenship to the children of illegal aliens. The ACLU, while it disputes the measure, wants Judge LaPlante, by forming a class action, to impose a nationwide halt to Mr. Trump’s policy. 

If the prospect of that kind of judicial overreach sounds familiar, it could be because the Supreme Court on June 27 ordered an end to the practice of “universal injunctions” issued by federal district judges. These nationwide diktats signaled the growing politicization of the judiciary, with 25 such halts issued just in the first 100 days of Mr. Trump’s second term. Senator Grassley calls them “a favorite tool for those seeking to obstruct Mr. Trump’s agenda.”

The Supreme Court, in Trump v. CASA, found that judges lack authority in law or the Constitution to issue these nationwide orders. “Universal injunctions were not a feature of federal court litigation until sometime in the 20th century,” Justice Amy Coney Barrett wrote for the majority. The first one was issued in 1963. Yet “by the end of the Biden administration,” she wrote, “almost every major presidential act” got “immediately frozen” by a federal judge. 

It’s to Judge LaPlante’s credit that when the birthright citizenship came before him earlier in the year, he pulled his punches, so to speak. While he sided with the opponents of Mr. Trump’s policy, he confined his ruling in February halting enforcement of the measure to the jurisdiction of his court — the federal district of New Hampshire. He did not seek to impose it nationwide via the kind of “universal injunction” that ran afoul of the high court.

Now, though, the ACLU is asking Judge LaPlante, in the case of Barbara v. Trump, to encompass the whole country by making the case a class action. The ACLU aims not only to include in the litigation the group of illegal alien parents who filed the suit before Judge LaPlante, but to form a “nationwide class of all other persons similarly situated.” To resolve the question, he will follow the rules of civil procedure, which cover the creation of such classes.

Neither we, nor, so far as we can tell, the Constitution, have an objection to Judge LaPlante recognizing a class within his district. If other federal district judges are asked to form classes and find themselves differing with the holding in Judge LaPlante’s district, the disputants could foreseeably take the dispute to an appeals court. If it turns out the circuits are in disagreement on this head, the question could well be settled by the Supreme Court.

Mr. Trump’s Justice Department, for its part, argues that the request to form a nationwide class is premature. Plus, too, DOJ urges Judge LaPlante to decline to “certify a nationwide class action” in light of Supreme Court precedent. In 1979, the Nine, in Califano v. Yamasaki, cautioned judges not to “certify a nationwide class” in cases where that could “interfere with the litigation of similar issues in other judicial districts.” Far-sighted fellows.

The fact that the non-citizens in the American Civil Liberty Union’s case are using pseudonyms to sue Mr. Trump also raises concerns about how they can adequately act on behalf of a prospective nationwide class, the DOJ reckons. In any event, Judge LaPlante could continue his instinct for judicial restraint in acting outside his district. A well-crafted opinion on this head could prove to be, as it were, a knockout.