"That’s not going to happen because the 14th Amendment says if you’re born here, you’re an American and you can’t kick Americans out. And then if you wanted to deport the people already here, each and every one are entitled to due process, and it would take decades to do that, and gazillions of dollars and the courts would block you at every turn. You must know all that," O'Reilly told Trump about his plans to stop automatically granting American citizenship to those born in the U.S. to those who are not citizens.
"Many lawyers are saying that’s not the way it is," Trump responded. "They are saying it is not going to hold up in court. Now, it’s going to have to be tested but they say it will not hold up in court."
When O'Reilly told Trump that he won't be able to deport people with American citizenship, Trump indicated that he doesn't believe the children of undocumented immigrants born in the U.S. are citizens.
"I don't think they have American citizenship and if you speak to some very, very good lawyers -- and I know some will disagree -- but many of them agree with me, you're going to find they do not have American citizenship," he said.
O'Reilly then asked Trump if he would favor a constitutional amendment to remove birthright citizenship. The presidential candidate said it would take too long.
"I’d much rather find out whether or not anchor babies are actually citizens," he said.
"Why don’t you test it now?” O'Reilly hit back. "You should do it tomorrow."
Watch O'Reilly's interview with Trump via Fox News: