It's useless to engage the specifically silly rhetoric by Donald Trump and others that might lead people to believe scores of pregnant Mexican women are waiting at the border to hop the fence and give birth in the United States.

That's because children who are born here cannot apply for their mothers to get legal residency until the citizen child turns 21. Therefore, the threat of "anchor babies" is political fiction, but the constitutional foundation of birthright citizenship is not.

While some politicians claim that birthright citizenship is a "policy" or a "law," I credit Trump, the GOP presidential front-runner, for knowing that it comes from the 14th Amendment. He has said he believes the amendment, which grew out of the Civil War carnage, has been misinterpreted and needs to be altered or challenged in the Supreme Court.

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The argument against birthright citizenship is that the 14th Amendment was ratified to overturn the Dred Scott decision denying blacks U.S. citizenship and that it should only apply to those who had been the victims of slavery. However, that is not how the amendment is written and it is not how it has been applied. Over the last two decades, clauses of the amendment have been invoked by the Supreme Court to award George W. Bush the 2000 election, overturn the Defense of Marriage Act, and require the elimination of university affirmative action programs that limit the number of white students. None of these decisions benefited former slaves.

The amendment's citizenship clause is straightforward: "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." Immigrants here illegally are subject to U.S. jurisdiction while they live here, and therefore their children born here are citizens.

The argument that the framers of the amendment never intended to protect anyone who had not been a slave, and particularly not immigrants, is easily countered by the clause's reference to naturalized citizens. The men who passed this amendment in 1868 lived during the greatest immigrant influx in American history. They were quite aware of the interplay between immigration and citizenship.

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The Supreme Court first addressed the issue of who is covered by the citizenship clause at a tumultuous time for immigration. Many Chinese immigrants had recently lost their legal status through the Chinese Exclusion Act of 1892. The court found that with the exception of the children of diplomats, enemy soldiers and Indians living "tribally," all other children born in the United States are citizens.

In its 1898 decision in the Chinese birthright citizenship case of U.S. v. Wong Kim Ark, the court noted that if the citizenship clause were not applied broadly, many people's citizenship would be called into question. We should take that warning to heart. If the 147-year-old interpretation is overturned, then people born in the United States -- like me -- might have to prove their parents had not come here illegally.

Birth certificates showing an American birthplace would no longer be enough to establish citizenship. We can imagine the scene at hospitals where mothers giving birth would have to carry their passports or green cards into the birthing rooms to make sure their children are recorded as citizens.

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The 14th Amendment is one of the noblest expansions of American freedom. Its framers understood the changing face of America in ways their fathers could not have. They saw America's future and they wanted everyone born here to be part of it.

Patrick Young is legal director of the immigrant advocacy group CARECEN and writes for Long Island Wins.