Harvard Law School professor emeritus and noted criminal defense attorney Alan Dershowitz alleges in an op-ed for The Hill that Jeff Zucker, president of CNN Worldwide, banned him from further appearances on the network because he defended President Donald Trump.

Dershowitz, while a liberal Democrat, and a supporter of Hillary Clinton in 2016, took the position that the president could not be charged with obstruction of justice based merely on an exercise of his constitutional duties. He was also critical of the investigation of Special Counsel Robert Mueller into claims of collusion between President Trump’s 2016 presidential campaign and the Russian government.

Dershowitz wrote Thursday that after several appearances in which he had debated CNN’s hosts and legal analysts over the various legal questions surrounding the “Russia collusion” controversy, he was never invited back again:

Viewers enjoyed my feisty debates with legal analyst Jeffrey Toobin and asked for more. Host Anderson Cooper enjoyed sparring with me, as did hosts Chris Cuomo and Don Lemon. CNN viewers benefited from evaluating my viewpoints against those of other guests and hosts. But then, suddenly, I was banned from CNN. Over the past half year or so, I have never once been asked to appear on a CNN program. Initially I wondered why, and I asked some of my friends at the network. They were evasive and studiously avoided any direct answer to my question. Then I received off-the-record information that an order had come from the very top: CNN executive Jeff Zucker didn’t want me on CNN any more. My centrist, nuanced perspective was anathema to CNN’s emerging brand as the anti-Trump network.

Since Special Counsel Robert Mueller concluded that there was, after all, no collusion, Zucker has defended the network’s coverage of story, telling the New York Times: “We are not investigators. We are journalists, and our role is to report the facts as we know them, which is exactly what we did.”

Read Dershowitz’s full op-ed here.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.