As mentioned yesterday, more than half of the Republicans running for their party’s presidential nomination have seconded Donald Trump’s call to end birthright citizenship. A number of them, in fact, have previously expressed support for the idea, and polls have found a majority of Americans support ending birthright citizenship. Last night, arguing with Bill O’Reilly, Trump took things a step further, contending that the Fourteenth Amendment does not actually establish birthright citizenship: “I don’t think they have American citizenship,” he said, referring to children born in this country to non-citizen parents. He is not the first to offer this interpretation; Harry Reid, the Senate minority leader, took the same view of things in the 1990s, although he has subsequently recanted.

There are a handful of Republicans publicly standing up for the Constitution: Rick Perry, Jeb Bush, Marco Rubio, and someone named George Pataki. But since they’re being outshouted at the moment let’s tackle this directly. Any child born in the United States is a citizen of the United States. The Fourteenth Amendment is clear. Here’s the relevant excerpt:

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.

The argument against the obvious interpretation of that sentence, as far as I can tell, hinges on the clause set off by commas—”and subject to the jurisdiction thereof.” The idea is that unauthorized immigrants, being unauthorized, are somehow not “subject to the jurisdiction” of the United States, and that they somehow transmit this unlawfulness to their children. To me, this seems like a strenuously backward interpretation. Unauthorized immigrants are obviously subject to the laws of the jurisdiction they happen to be in; that’s why they’re referred to as “illegal” or, as I prefer, “unauthorized.”

For an expert analysis, though, let me recommend this 2006 piece from James C. Ho, who succeeded Ted Cruz as solicitor general of Texas under Attorney General Greg Abbott. He concluded that the Fourteenth Amendment establishes birthright citizenship; that it was clearly intended to do so; and that the provision can only be altered by constitutional amendment, rather than by statute (or Trumpian decree). “The Citizenship Clause was no legal innovation,” Ho noted. “It simply restored the longstanding English common law doctrine of jus soli, or citizenship by place of birth.”

I’d also like to refer readers to Greg Sargent, at the Washington Post, who argues that it’s a shame Republicans are agitating for an end to birthright citizenship, and an ironic shame because this is one of the party’s greatest historical accomplishments. He consulted the historian Eric Foner—probably the country’s foremost authority on the Reconstruction—for insights on passage of the Fourteenth Amendment:

“The Civil War and the emancipation of the slaves shaped the Republican Party and pushed it in the direction of nationalism, inclusiveness, and openness,” Foner says. “The idea was that citizenship should be extended to people regardless of accidental characteristics, such as race, national origin, or the status of their parents. This established a national standard for citizenship. The principle was one of opportunity and inclusiveness. That’s what the Republican Party stood for. The 14th amendment became one of the defining principles of the Republican Party.”

The Constitution is clear, in other words, and so is American history. I can understand why some Americans would want to revisit the issue. The world has changed a lot since the 19th century and, in particular, technological change has obviously facilitated geographic mobility that would have been unimaginable back then. About 13 percent of people living in America are foreign-born; that’s not unprecedented for our country, although it is relatively high by international standards. And the fact that the United States has birthright citizenship is relatively unusual. It’s becoming more rare, too: in recent years several countries with similar roots in English common law—Australia, New Zealand, Ireland—have revised their own jus soli provisions.

But the United States is an unusual country—an exceptional one, even. As I argued on the Fourth of July, our enduring commitment to impractical ideals is what makes us great. Values aside, as a practical matter, the only common denominator of American citizenship is citizenship itself. And politically, this is dangerous territory for Republicans. They’re presumably aggrieved about “anchor babies” or “birth tourism,” but they’re implicating a vast swathe of people. There are millions of Americans with at least one foreign-born parent. I’m one of them, and my citizenship status is not subject to debate: I was born in the United States, end of story. And again, Trump remains the frontrunner for the Republican presidential nomination: no reasonable adult can think it’s a good idea to meddle with the Constitution as long as that’s the case.