Leading Republicans have gotten chilly toward the Constitution’s 14th Amendment, which guarantees citizenship to people born in the United States. Senators Mitch McConnell, John McCain, Lindsey Graham, Jeff Sessions and Jon Kyl have been suggesting that the country should take a look at it, re-examine it, think it over, hold hearings. They seem worried that maybe we got something wrong nearly 150 years ago, after fighting the Civil War, freeing enslaved Africans and declaring that they and their descendants were not property or partial persons, but free and full Americans.

As statements of core values go, the 14th Amendment is a keeper. It decreed, belatedly, that citizenship is not a question of race, color, beliefs, wealth, political status or bloodline. It cannot fall prey to political whims or debates over who is worthy to be an American. “All persons born or naturalized in the United States, and subject to the jurisdiction thereof,” it says, “are citizens of the United States and of the State wherein they reside.”

People like Mr. Sessions, who pride themselves on getting the Constitution just right (on, say, guns), are finding this language too confusing. “I’m not sure exactly what the drafters of the amendment had in mind,” said Mr. Sessions, the top Republican on the Judiciary Committee, “but I doubt it was that somebody could fly in from Brazil and have a child and fly back home with that child, and that child is forever an American citizen.”

It’s true that air travel was not a big focus in 1868, but this is not about a horde of pregnant jet-setting Brazilians, if, indeed, such a thing even exists. The targets are Mexicans, and the other mostly Spanish-speaking people who are the subjects of a spurious campaign against “anchor babies”  children of illegal immigrants supposedly brought forth to invade and occupy.