The Justice Department, however, has limited jurisdiction over former employees. They can investigate but the remedy in the event of finding wrongdoing would be to make a note in Comey's file should he ever seek to be employed by the Justice Department again.
As a businessman, Trump had a long history of threatening legal action. But the businessman-turned-president rarely followed through on those claims.
During the 2016 campaign, Trump threatened to sue Sen. Ted Cruz, his primary opponent, multiple times, along with the Republican Party of Louisiana, The Washington Post, The New York Times and the women who accused him of sexual misconduct.
None of those lawsuits were ever filed.
The new complaint will focus on Comey's testimony that he gave a friend the content of memos about his conversations with Trump and asked the friend to then give that information to a reporter. Comey said Friday that he gave the friend -- later identified as Daniel Richman, a longtime Comey confidante and Columbia University professor -- the information after Trump tweeted that he may have tapes of his conversations with the fired FBI director.
"My judgment was I needed to get that out into the public square. So I asked a friend of mine to share the content of the memo with a reporter," Comey said Thursday.
Trump's attorney, Marc Kasowitz, could file the complaints early next week, one source said.
Republicans have looked to discredit Comey by calling him a "leaker" because of the way he disseminated the information about Trump.
Comey said Thursday that the memos he wrote were unclassified. Disseminating unclassified information is generally not considered leaking and the President did not assert executive privilege over Comey's testimony.
The President himself accused Comey of lying and leaking Friday on Twitter.
"Despite so many false statements and lies, total and complete vindication...and WOW, Comey is a leaker!" Trump tweeted Friday morning.
The source said the fact that Comey decided to disseminate the information because of a tweet was "gold" for the lawyers looking to file a complaint against the former FBI director.
Norm Eisen, former White House Ethics czar for President Barack Obama, told CNN that Comey "did nothing improper in disclosing the details of the meeting in which Trump ordered him to drop the investigation against Flynn."
"The conversation was not classified, and neither was the memo about it," Eisen, a CNN political commentator, said. "DOJ rules do not prohibit the disclosure of such information. The conversation was not subject to the attorney-client privilege or other privileges since Comey was obviously not acting as Trump's lawyer. And if any privileges did apply, Trump waived them by repeatedly disclosing the contents of his conversations with Comey."
Eisen also suggested on Twitter that Kasowitz may be abusing his power as a lawyer.
"There can also be bar penalties for abuse of process, and civil ones for libel," he said. "But we need to let this play out more before those assessments are made."
Laurence Tribe, a professor of constitutional law at Harvard Law School, said that the "only impropriety, and perhaps illegality, in connection with the Comey release of his conversation with the President and of the memo recording was that of Trump, threatening the former FBI Director through Marc Kasowitz yesterday."