Former acting Attorney General Sally Yates testifies during the Senate Judiciary, Subcommittee on Crime and Terrorism hearing on Russian Interference in the 2016 United States Election on Monday, May 8, 2017.

Former acting Attorney General Sally Yates has suggested that former national security advisor Michael Flynn may have run afoul of criminal law before he got fired.

In an excerpt of a CNN interview that will air Tuesday, Yates said "there is certainly a criminal statute that was implicated by [Flynn's] conduct." She did not specify what that law may have been.

A person close to Flynn said that Yates seemed to hint that Flynn could have violated the Logan Act, an obscure law essentially saying private citizens cannot conduct foreign policy discussions without the government's permission. It would be a stretch to argue that Flynn broke that law as he prepared to become national security advisor, the person said.

Yates says she warned the White House in late January that Flynn — a retired Army lieutenant general — "essentially could be blackmailed" by Russia after he misled top officials about the nature of December conversations he had with that country's ambassador to the United States. Yates previously said it created a "compromise situation," but Donald Trump did not fire Flynn until 18 days after the White House was first warned.