US President Donald Trump's claim that he can unilaterally end the primogeniture rights of US citizenship is likely to face strong opposition from the courts.
The Supreme Court said 120 years ago that the Constitution automatically grants citizenship to children born in the US, with few exceptions, even though their parents are not citizens.
Although a handful of lawyers say the Congress could pass a law to change that rule, this is far from the President's claim in an interview Axios at HBO that he can do it through an executive order.
"There is an active academic debate about whether mere legislation could change this with respect to illegal immigrants and tourists – probably not, although there are good arguments on both sides," said Ilya Shapiro, senior officer of the libertarian Cato Institute.
"But regardless, it's not something that can be achieved by executive action alone."
The issue deals with the 14th Amendment to the Constitution, which was adopted after the Civil War to protect the rights of newly freed slaves.
The change grants citizenship to anyone born in the US who is "subject to his jurisdiction".
The question of first-birth citizenship had previously come before the Supreme Court, especially in a case of 1898, "United States vs. Wong Kim Ark".
"It's ridiculous and must end": Trump threatens to cancel automatic citizenship for children of US-born foreigners
Wong Kim Ark was born in California in 1873 to parents who came from China to the United States.
After visiting China, Wong Kim Ark was denied re-entry into the United States in 1895 under Chinese exclusion laws.
However, the Supreme Court ruled that the actions did not apply to Wong Kim Ark and that he was a US citizen due to his birth in the United States.
The court referred to "the old and fundamental rule of citizenship from birth in the territory", which includes the provision "all children born here of alien foreigners", with the exception of American Indians, diplomats and members of the invading armies.
This decision was not addressed directly to persons who had entered the country illegally, but the court touched on this issue in a 1982 ruling in which school districts were required to register unauthorized immigrants.
In a footnote, the court said it could not be "made a plausible distinction" to disqualify the children of undocumented immigrants from first birth.
Some prominent conservatives claim that the matter is regulated without a constitutional amendment.
James Ho, now a federal appointee appointed by Trump, wrote in 2011 that the wording of the 14th Amendment leaves no doubt that the children are being held by undocumented migrants.
"The clear meaning of this language is clear," wrote Ho, who was the Attorney General of Texas at the time.
"A foreigner living in the United States is under his jurisdiction" because he has a legal obligation to comply with US law. "
John Yoo, a former Justice Department official of President George W. Bush, made a similar assessment last week.
"After reading his text, structure, and history, anyone born on American territory, regardless of their national origin, ethnic origin, or status in life, is an American citizen," Yoo wrote for the American Enterprise Institute.
House spokesman Paul Ryan said the April 14 amendment was "pretty clear" in its coverage of undocumented immigrants.
"You can not end your first-born citizenship with an executive order," Ryan said.
Even if the 14th amendment was read as missing the children of undocumented immigrants, Congress would have to amend the federal law that was drafted to codify the conventional understanding, said Michael Dorf, professor of constitutional law at Cornell Law School.
Currently, "even if the constitution would allow Congress to deprive such persons of citizenship, this would not allow the President to do so because that would violate the Statute," Dorf said.
Saikrishna Prakash, a professor of law at the University of Virginia, said the language in previous Supreme Court rulings could help Trump explain the case that undocumented immigrants are not subject to United States "jurisdiction". But Prakash said Trump could not change conventional understanding alone.
Trump "can not just decide who a first-born citizen is," he said.
"Those who believe they qualify will make a decision from the courts."
Also, one of the leading proponents of the reinterpretation of the 14th Amendment, Professor Peter Schuck, the Yale Law School, said Trump's idea for a leadership order was not based on.
"Trump obviously can not do this from EO – and I am confident that no competent lawyer would advise him otherwise," said Schuck, who in 1985 wrote a book on the subject.
"This is just pre-election policy and misrepresentation and should be harshly criticized as such."
Additional reporting from Agence France-Presse