CNN host Brian Stelter pressed attorney and legal scholar Alan Dershowitz on Sunday about whether President Trump asked him to be his attorney, in what became a heated sparring.

“I can’t ever say who’s ever asked me to be his lawyer, but I’ve made it clear: I don’t want to be the president’s lawyer,” the Harvard professor said.

“I think he got a good lawyer in New York, I think he has some good lawyers in Washington,” he continued. “There’s a lot of conflicts of interest, which make it very hard for him to get lawyers. I know that a lot of good lawyers who want to get involved in the case, their law firms won’t let them because they have conflicting interests, but I think the key point is to make sure that in an effort to get Trump, we don’t diminish our civil liberties.”

Dershowitz lambasted the raid on Michael Cohen and said he was disappointed that groups like the ACLU aren’t standing up more to protections of things like attorney-client privilege.

“I don’t want to communicate in any other way,” he said. “I do not want to be his lawyer, I don’t want to give him legal advice, I can’t give legal advice on a one-to-one basis. I can only state what I believe are the constitutional issues on national television. One of the reasons I don’t want to be his lawyer is because I have no interest in what happened to him before he became president, his business life, his personal life. I’m only interested in the Article 2 issues, the constitutional issues. I’m interested in doing what the American Civil Liberties Union has failed to do, and that is defending the rights of all Americans.”

But Stelter pushed back, pressing him for more details on his interactions with the president.

“I have seen him twice as president, mostly for handshakes and one phone call,” Dershowitz explained. “We’re not friends. I’ve never been in a social setting with him at all, so he would never show me his feelings. I’m somebody brought in from the outside to help him on the Middle East and then go home…I am not a supporter. I am not a defender of Donald Trump the person. I’m a defender of civil liberties and basic due process.”