President Donald Trump is proposing removing the right to U.S. citizenship for children born to noncitizens on U.S. soil—a move that could spark fierce debate over the Fourteenth Amendment and American identity. In a new interview with Axios, the president said he intends to revoke birthright citizenship through an executive order.

“It was always told to me that you needed a constitutional amendment. Guess what? You don’t,” Trump said in the interview, part of which aired Tuesday morning. He continued: “You can definitely do it with an act of Congress. But now they’re saying I can do it just with an executive order.”

This isn’t the first time the president has suggested he’d like to end the right. In 2015, then-candidate Trump also expressed an intent to end birthright citizenship, calling it “the biggest magnet for illegal immigration.” His stated intent takes direct aim at the Constitution and the millions of people who were born in the United States to immigrant parents.

“This is one of the longest-standing debates under the Constitution,” said Jonathan Turley, a law professor at George Washington University. The Fourteenth Amendment says 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.” That clause “has proven to be maddening since it was written,” Turley said. “Various people who were involved in drafting the Fourteenth Amendment suggested that this was a condition that people be citizens or at least legal residents in the United States to be ‘subject to the jurisdiction thereof.’”