By Peter Grier Peter Grier â€“ Wed Aug 11, 5:14 pm ET Washington â€“ Is â€œbirthright citizenshipâ€ â€“ the policy of granting US citizenship to every child born on national soil â€“ really enshrined in the US Constitution? Some experts believe it isnâ€™t. Congress, they say, could regulate who qualifies for birthright citizenship via legislation, within limits. Lawmakers might deny it to children born in the US to illegal immigrants, for example. This could be an important legal distinction. Circumscribing birthright citizenship with a bill would be very difficult, particularly while President Obama remains in office. But doing the same thing via the direct route of amending the Constitution would be virtually impossible. â€œWe do not need to amend the Constitution to end birthright citizenship,â€ said Rep. Lamar Smith (R) of Texas in a statement issued Tuesday. Birthright citizenship is a hot topic in Washington nowadays because some congressional Republicans have become increasingly vocal about a desire to deny such status to the children of parents who are residing in the US illegally. The GOP leaders of both the House and Senate have said they favor holding hearings on the issue, at the least. Many legal scholars believe that changing the policy would require changing the 14th Amendment to the Constitution, on which birthright citizenship is based. But â€œmanyâ€ legal scholars is not the same thing as â€œall.â€ Section 1 of the 14th Amendment begins this way: Ã¢â‚¬Å“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 key phrase here is subject to the jurisdiction thereof. Illegal immigrants are not subject to US jurisdiction, in the sense that they cannot be drafted into the US military or tried for treason against the US, said John Eastman, a professor at the Chapman University School of Law, in a media conference call Monday. Their children would share that status, via citizenship in their parentsâ€™ nation or nations of birth â€“ and so would not be eligible for a US passport, even if born on US soil, according to Dr. Eastman. Furthermore, federal courts have upheld the right of Congress to regulate naturalization policies over and above the basic constitutional guarantee, according to Eastman. Taken together, he says, all this means lawmakers, if they choose, could deny birthright citizenship to the children of parents here illegally. Ã¢â‚¬Å“The 14th Amendment is a floor, but how far above that floor we go is a matter of basic policy judgment that our Constitution assigns exclusively to the Congress of the United States,Ã¢â‚¬ Perhaps the defining Supreme Court ruling in this area is US v. Wong Kim Ark, an 1898 case in which justices upheld the US citizenship of a child born on US soil to Chinese immigrant parents. The parents were in the US legally, however. â€œThe courts apparently have never ruled on the specific [issue] of whether the native-born child of illegal aliens as opposed to the child of lawfully present aliens may be a US citizen,â€ concludes a 2005 Congressional Research Service report on birthright citizenship. Defenders of the current US interpretation of birthright citizenship say that a century of legal precedents supports their view that it is defined by the Constitution itself and is beyond the reach of congressional reinterpretation. The wording of the 14th Amendment means what it says, they say. The â€œsubject to the jurisdictionâ€ phrase today excludes the children of diplomats, who are immune from most US civil and criminal laws by treaty. â€œThose who want to read it narrowly ... are simply wrong,â€ said Elizabeth Wydra, chief counsel of the Constitutional Accountability Center, in a recent conference call.