“Blatantly unconstitutional” is how a federal judge is describing President Trump’s executive order scaling back so-called “birthright citizenship.” The ruling isn’t likely to be the final word, though, in a matter that now will be weighed at the district court level and then, possibly, work its way to the Supreme Court. That would offer a chance to clarify the birthright question, which has been murky since the ratification in 1868 of the 14th Amendment.

That’s where the Constitution states that “All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.” Those words in the middle — “and subject to the jurisdiction thereof” — are at the crux of the dispute. Liberals, per a 19th-century Supreme Court ruling and longtime interpretation of federal naturalization law, tend to ignore the constitutional caveat.

We marked the importance of the jurisdiction clause in an editorial called “Trump Vows To End Birthright Citizenship” that appeared in these columns in December. We marked “the sense that this question isn’t fully settled in our search for a more-perfect union.” After all, the Supreme Court has never tackled the question head-on. The closest case, United States v. Wong Kim Ark, from 1898, touched on the citizenship of a child of legal residents.

Conservatives and other critics of unsanctioned, or even open, immigration point to the 14th Amendment’s wording about “jurisdiction” to suggest that children born to illegals shouldn’t be automatically granted citizenship. That thinking animates Mr. Trump’s order, which contends that the 14th Amendment “has never been interpreted to extend citizenship universally to everyone born within the United States.”

Yet since Wong Kim Ark, the Congressional Research Service says, “the prevailing view has been that all persons born in the United States are constitutionally guaranteed citizenship at birth unless their parents are foreign diplomats, members of occupying foreign forces, or members of Indian tribes.” The closest the Nine came to reappraising the question arose in 1982, when the court found that states cannot deny public education to the children of illegals.

That was in the case of Plyler v. Doe, which relied on the 14th Amendment’s Equal Protection Clause. Plyler, though, was decided by a narrow majority of five to four, and could prove ripe for reevaluation by a more conservative court. That’s especially true in light of the increasing strain that unchecked illegal migration — some 5 million persons just since 2021 — has imposed on state and local budgets.

Critics of “birthright” also point to Wong Kim Ark’s dissenters, Chief Justice Melville Fuller and Justice John Harlan, who denied that children of non-citizens were automatically entitled to citizenship. “The children of aliens,” they said, “must necessarily remain themselves subject to the same sovereignty as their parents, and cannot, in the nature of things, be, any more than their parents, completely subject to the jurisdiction of such other country.”

That reasoning could get a new hearing in the federal courts as Mr. Trump’s order is weighed. Today’s ruling — a temporary halt issued by Judge John Coughenour at Seattle — comes in but one of the five federal lawsuits that have already been filed against the order. “The president cannot, with a stroke of a pen, write the 14th Amendment out of existence, period,” New Jersey’s attorney general, Matt Platkin, avers in a lawsuit filed in Massachusetts.

Mr. Platkin’s hyperbole points to a potential weakness in Mr. Trump’s position — his attempt to change federal policy by decree. Considering the import of this question, and longstanding legal precedent, it would be more effective were Congress to use its granted power over naturalization law to clarify the meaning of the 14th Amendment. Plus, too, there’s always the option to amend the Constitution to try to get the wording the way the states want it.