Former White House national security adviser Michael Flynn pleaded guilty Friday to lying to the FBI about contacts with Russia’s former ambassador to the U.S., admitting he violated a law that also criminalizes lying to Congress.

Scholars have mixed views on whether Flynn’s guilty plea is bad news for Attorney General Jeff Sessions, who allegedly lied to Congress about his contacts with the same ambassador.

Harvard Law School professor Lawrence Tribe told the Washington Examiner that Sessions should be concerned about facing the same charge as Flynn.

“Of course he should," Tribe said.

But Harvard Law School professor emeritus Alan Dershowitz said he's not so sure, raising questions about proof of intent.

In January, the same month Flynn misled the FBI, Sessions told senators in written and oral responses that he knew of no Trump campaign contacts with Russia and that he had none himself.

“I’m not aware of any of those activities,” Sessions told Sen. Al Franken, D-Minn., who asked if “anyone affiliated with the Trump campaign communicated with the Russian government in the course of this campaign.”

Sessions added: “I did not have communications with the Russians.”

In a written answer, Sessions told Sen. Patrick Leahy, D-Vt., “no,” he had not “been in contact with anyone connected to any part of the Russian government about the 2016 election, either before or after Election Day.”

It later emerged that Sessions met with Russian Ambassador Sergey Kislyak in his Senate office in September 2016, after they also met during the Republican National Convention in July 2016.

Sessions defenders argue the questions were unclear. Justice Department spokeswoman Sarah Isgur Flores said there was “absolutely nothing misleading," and Sessions stressed he “never met with any Russian officials to discuss issues of the campaign.”

Questions about the accuracy of Sessions’ testimony deepened, however, in October after Trump campaign adviser George Papadopolous pleaded guilty to lying to the FBI. Papadopolous reportedly said at a March 2016 meeting with Sessions that he could establish contact with Russian President Vladimir Putin.

Sessions told lawmakers that he forgot about that meeting with Papadopolous.

Lying to Congress is rarely prosecuted, but there are some recent examples.

In 2007, second-ranking Interior Department official J. Steven Griles pleaded guilty to lying to senators about his links to lobbyist Jack Abramoff. Baseball player Miguel Tejada pleaded guilty to lying to Congress in 2009 after giving false testimony in 2005 about performance-enhancing drugs. Player Roger Clemens was acquitted in 2012 of similarly lying to Congress.

Special counsel Robert Mueller, who is leading the investigation that resulted in Flynn's plea, has shown no qualms about using rarely enforced laws in his probe of Russia's links to Trump aides.

Mueller's team dusted off the Foreign Agents Registration Act to indict former Trump campaign manager Paul Manafort and assistant Rick Gates in October for pre-campaign work with Ukrainian politicians. There were fewer than 10 FARA prosecutions and just one conviction between 1966 and 2015, according to the Justice Department inspector general's office.

Although it’s unclear what Sessions has told the FBI about his or the campaign's contact with Russia, Tribe said that his congressional testimony alone may be enough for a prosecution under the same law that Flynn admitted violating.

“Very likely yes, assuming [there is] sufficiently persuasive proof that Sessions knew he was giving materially false and misleading answers,” Tribe said.

Finding enough proof to win a conviction, however, may be difficult.

“They would have to prove a direct knowing lie,” Dershowitz said, something that’s “hard to do.”

Dershowitz said “I haven’t seen anything” that would offer enough proof. "He’s careful."