Former New York City Mayor Rudy was put on notice that he must retract his allegations that the Lincoln Project was responsible for organizing the fatal Jan. 6 insurrection at the U.S. Capitol.
On Friday, Giuliani blamed the Lincoln Project for the riots by Trump supporters during an appearance on Steve Bannon's podcast.
Giuliani suggested that insurrection was a false flag operation, saying that it was "wolves in sheep's clothing" that were behind the insurrection.
The Lincoln Project responded on Saturday with a three-page letter from attorney Matthew T. Sanderson of Caplin & Drysdale.
The entire first page of the letter was just Drysdale recounting a list of reasons Giuliani has lost credibility.
The letter harshly criticizes Giuliani for pushing the election fraud lie that incited the insurrection.
"You told your zealots what to do. They listened. They vandalized. They terrorized. They injured. They killed," the letter reads. "Rather than apologizing for your actions, you have spent the ensuing weeks deflecting blame and grasping for some way to explain your misconduct."
The letter then details Giuliani's allegations on Bannon's podcast.
"You committed a textbook act of defamation. You publicly accused The Lincoln Project of an infamous and criminal act that it had nothing to do with, as you very well know. You lied," the letter charges.
"You have until Wednesday, February 3rd to retract your statement fully and to apologize publicly to The Lincoln Project," the letter warned. "Refuse at your peril."