Comey, fired by Trump last month, is scheduled to testify before the Senate intelligence committee on Thursday. Whatever Comey tells Congress isn't going to get Trump in legal trouble, so the White House has seemingly (and wisely) concluded that it's just better to get past it quickly.
Last month, the New York Times reported that Comey wrote a February memo alleging Trump asked him to shut down the FBI investigation into Flynn's ties to Russian Federation.
The move means Mr Mueller's politically-charged inquiry will now look into Mr Flynn's paid work as a lobbyist for a Turkish businessman a year ago, in addition to contacts between Russian officials and Mr Flynn and other Trump associates during and after the Nov 8 presidential election.
"I think the president has effectively waived the privilege in this case because he has communicated publicly, in several different public formats, about his conversations with Mr. Comey", said Mark Rozell, an expert on executive privilege and the dean of the Schar School of Policy and Government at George Mason University in Virginia.
Ohlin said that if Trump invokes executive privilege and Comey testifies despite that, the administration has two avenues for recourse: an injunction before Comey's testimony, or a prosecution afterward, neither of which would be very helpful for Trump.
Trump has called an FBI investigation into alleged ties between his campaign and Russian Federation a "witch hunt" created to undermine the legitimacy of his 2016 election win.
"I don't think it's appropriate for Trump to claim executive privilege after he's been writing and tweeting about his conversations with Comey". Trump undercut that narrative just days later by saying he dismissed Comey in part because of the "Russia thing".
The White House has left open the question of whether Trump would intercede in order to scuttle Comey's testimony.
Asked whether Comey was ever given a chance to make that pledge, or ever told by Rosenstein or Sessions that his actions were wrong, a Justice Department spokeswoman said, "I won't comment on that". Trump can not use executive privilege to keep Comey from testifying about discussions that may point to potential misconduct, and that's especially true now that Trump has already made those discussions public.
The scope of Comey's testimony was not exactly clear, though Mueller was permitting him to speak publicly, an associate told the AP.
"Does Mr. Comey agree that that is what was said?"
"If I were his attorney, my advice would be: Mr. President, if you've done nothing wrong and have nothing to hide, cooperate with the investigation, be completely transparent, you have nothing to be afraid of, ' " he said. Separately, a group of supporters rallied near the White House to support the president's decision to withdraw from the Paris climate accord.
Executive privilege is a doctrine that has developed over time to allow a president to communicate freely with his Cabinet members and staff about national security issues and other sensitive matters without being concerned those discussions would be disclosed to Congress, the courts or the public.
Comey is also likely to be asked by lawmakers about Trump's assertion that the former FBI chief told him three times that he was not under investigation as part of the federal probe into his campaign's possible Russian Federation ties.