President Donald Trump defended his idea to end birthright citizenship for illegal immigrants by executive order, in a Wednesday tweet.

So-called Birthright Citizenship, which costs our Country billions of dollars and is very unfair to our citizens, will be ended one way or the other. It is not covered by the 14th Amendment because of the words “subject to the jurisdiction thereof.” Many legal scholars agree…..

— Donald J. Trump (@realDonaldTrump) October 31, 2018

Trump told Axios Monday evening he will issue a future executive order to end birthright citizenship for illegal immigrants and some other non-citizens, adding “it was always told to me that you needed a constitutional amendment. Guess what? You don’t.”

“We’re the only country in the world where a person comes in and has a baby, and the baby is essentially a citizen of the United States … with all of those benefits,” Trump continued. The president’s expected executive order is certain to spark a high stakes legal battle, which is likely to make it all the way to the Supreme Court.

Birthright citizenship stems from the 14th Amendment of the Constitution which states that “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.”

Existing judicial precedent, however, only clarifies that children of lawful permanent residents in the U.S. qualify for citizenship with no ruling on the children of illegal immigrants or temporary residents. Any executive order by Trump would only be able to legally target these immigrant populations.