President Donald Trump's assertion that the U.S. “citizen by birth” tradition can be changed by executive order rather than constitutional amendment or legislative act has set off a wave of legal analysis by scholars and pundits scrambling to piece together the legal basis for this existential principle of U.S. individual rights.

The president's assertion that he can, and will, disavow the ingrained U.S. cultural tradition (as well as legal mandate) that birth on U.S. soil renders citizen stature, with only a few historic exceptions, deserves careful analysis, if only because the birthright of citizenship has been so sacred to Americans across the political spectrum.

Trump acknowledges he is aware of contrary views: “It was always told to me that you needed a constitutional amendment. Guess what? You don't. You can definitely do it with an act of Congress. But now they're saying I can do it just with an executive order.” Given that assertion, Trump seemed almost demure by later noting, “This will be decided by the Supreme Court.”

The president, the pundits and plenty of legal scholars have weighed in with theories on why citizenship attaches at birth or why the president can (or cannot) change that right by executive order. Most comments focus on the 14th Amendment, which was added in 1868, to clarify the status of newly emancipated slaves. While instructive, the 14th Amendment is not the birthplace of “birth citizen” rights.

The former head of the White House Office of legal Counsel testified before Congress in 1995 that even before the 14th Amendment to the U.S. Constitution was enacted, U.S. law contained ample evidence of what the framers meant to be qualifiers for U.S. citizenship.

The Constitution does not expressly define citizenship, he told a congressional hearing, “every child born within the territory of alien parents was a natural-born subject, with the exception of children born of foreign ambassadors, of alien enemies during hostile occupation, and of aliens on a foreign vessel,” Walter Dellinger told Congress.

That testimony was solicited because both the Senate and the House of Representatives in 2015, at the time both under Republican control, tried to do legislatively exactly what Trump is proposing by executive order. Both houses proposed legislation to amend the Immigration and Nationality Act to exclude undocumented or illegal alien parents from bestowing the right to automatic citizenship at birth in the United States. The bills stalled in committee.

Birthright citizenship bills have been introduced under GOP and Democratic presidents since 2007, and have never been voted out of committee.

What the Supreme Court Says

Several Supreme Court decisions have been clear that the children born in the U.S. (whether the parents are foreign nationals with visas or undocumented or illegal aliens) are entitled to citizenship. There have been a few exceptions including foreign diplomats, alien enemies and until 1924, Native Americans. Otherwise, citizenship belongs to the natural born child, pedigree notwithstanding.

The most relevant case, United States v. Wong Kim Ark, defined those included and those exempted when it held:

“The 14th Amendment affirms the ancient and fundamental rule of citizenship by birth within the territory, in the allegiance and under the protection of the country, including all children here born of resident aliens, with the exceptions or qualifications (as old as the rule itself) of children of foreign sovereigns or their ministers, or born on foreign public ships, or of enemies within and during a hostile occupation of part of our territory, and with the single additional exception of children of members of the Indian tribes owing direct allegiance to their several tribes.”

In the Wong Kim Ark case, justices with the majority and in the dissent reflected on what America stands for in terms of a person belonging to the nation. That is because, before the Civil War, the Civil Rights Act of 1866, and the 14th Amendment, there was definition on the federal level of the requirements of citizenship. The enactment of the amendment changed everything. It was no longer a federation of states, insofar as citizenship was concerned.

In that opinion and in the dissent, the justices discussed what citizenship meant to the framers, defined in English common law. The debate appears to frame a discussion of what is today the countries that do accept jus soli (around 34 nations, mainly North and South America) and those who follow jus sanguinis (the rest of the world).

Judge James C. Ho of the U.S. Court of Appeals for the Fifth Circuit, a Trump appointee, said that efforts to rewrite U.S. citizenship law without a constitutional amendment are a losing court battle, writing in 2006 that birthright citizenship is guaranteed to “descendants of Mayflower passengers” as it is to “children of undocumented workers.”

The old world, born of parentage, inheritance and monarchies, and the new world, created as a revolutionary melting pot.

The president flagged the argument that his lawyers will make in a tweet: “So-called Birthright Citizenship … is not covered by the 14th Amendment because of the words 'subject to the jurisdiction thereof.”

Constitutional scholars and policymakers differ on what a strict constructionist or originalist interpretation of the Constitution would say, if challenged today.

The former director of the public liaison office in the Reagan White House, Linda Chavez wrote in a 2010 Wall Street Journal op-ed: “Conservatives should not betray these values based on a misreading of American history and legal precedent. Instead of amending the Constitution to eliminate 'anchor babies'— the ugly term opponents of birthright citizenship use to describe these U.S. citizens —Republicans should be helping them become good Americans.”

Although the Wong Kim Ark case, to be sure, appears to address the issue squarely, the facts of the case deal with a U.S. resident parent, not an illegal migrant.

Other Supreme Court cases have been clear on aspects of the issue. In Afroyim v. Rusk, the court held that a U.S. citizen cannot inadvertently lose citizenship. Afroyim held, “The Fourteenth Amendment, while it leaves the power where it was before, in Congress, to regulate naturalization, has conferred no authority upon Congress to restrict the effect of birth.”

A more recent case, Plyler v. Doe, decided in 1982, held that undocumented school-age children were entitled to free public education, and stated that the 14th Amendment's phrase within its jurisdiction “cannot be distinguished on the asserted ground that persons who have entered the country illegally are not within the jurisdiction of a state even if they are present within its boundaries and subject to its laws.”

In addition to the Supreme Court, the lower courts have not only upheld the rights of citizen children born to recent illegal aliens, but have held that their non-citizen parents would not be deported, mainly on hardship exemptions.

Yet, the debate has had many constitutional scholars reflecting on what the framers meant, both in the Constitution itself and in the 14th Amendment.

Michael Anton, a lecturer at Hillsdale College and a former Trump administration official, wrote in a Washington Post column that the court ruled in the Wong Kim Ark case that “only that children of legal residents are citizens. That doesn't change the status of children born to people living here illegally.”

Some legal analysts think the issue in the courts is the executive trying to make a constitutional change by fiat.

“Trying to ram through that change by Executive Order makes it even harder to defend legally and is also bad governance,” said Matthew Waxman, a law professor at Columbia Law School who served in the George W. Bush Administration.

As to the political realities, the number of babies born to unauthorized immigrant parents in the U.S. fell to 250,000 in 2016, the lowest figure since 2000.

The Supreme Court has been philosophical about the issue, looking at the difference between jus soli, citizenship by “right of the soil” under English common law, and jus sanguinis, the inheritance of citizenship though parental bloodlines.

In the end, the Supreme Court, as Trump said, will likely hear the case, based on the simple words of the 14th Amendment: “All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the states wherein they reside.”

What the courts decide, should the president go ahead with his plan, may well shape how the melting pot sees itself.

Pamela Falk reports for CBS News from the U.N. and was staff director of a congressional subcommittee. She is a Columbia Law grad and can be reached at [email protected] or @pamelaFalk.