President Trump's threats to revoke broadcast licenses for television stations that publish content he disapproves of has led to mounting criticism for Federal Communications Commission Chairman Ajit Pai and fellow Republican commissioners, who are "in a Catch 22" over how and whether to respond to the president's comments.

This month, Trump, lashing out at "fake news" published by NBC and other networks, questioned on Twitter "at what point is it appropriate to challenge their License?"

"Network news has become so partisan, distorted and fake that licenses must be challenged and, if appropriate, revoked," Trump said in a second tweet. "Not fair to the public!"

Since Trump tweeted his threats to revoke broadcast licenses, Pai and Republican FCC commissioners have fielded calls from Democrats to disavow the president's comments.

Democratic Reps. Frank Pallone of New Jersey and Mike Doyle of Pennsylvania, top Democrats on the House Energy and Commerce Committee, asked all five FCC commissioners to appear before the committee to address Trump's comments.

Then, last week, a trio of Democrats on the Senate Commerce Committee called for an oversight hearing on Trump's threats to broadcast licenses, and criticized Pai for his delayed response to the president.

"The FCC chairman's failure to quickly respond and denounce these threats is shocking and raises questions about the ability of the FCC to truly act independently under Chairman Pai's leadership," Democratic Sens. Brian Schatz of Hawaii, Tom Udall of New Mexico, and Maggie Hassan of New Hampshire wrote. "It is imperative that FCC Chairman Pai and his fellow commissioners address this committee and respond to the president's stated desire for regulatory abuse of his perceived critics at the FCC."

Democratic FCC Commissioner Jessica Rosenworcel also urged Pai to condemn Trump's threats to revoke broadcast licenses.

"History won't be kind to silence," she told CNN.

Pai addressed Trump's tweets during an event hosted by the Mercatus Center at George Mason University on Tuesday, and said the FCC doesn't have the power to revoke a broadcast license based on the "content of a particular newscast."

"I believe in the First Amendment," Pai said. "The FCC, under my leadership, will stand for the First Amendment. Under the law, the FCC does not have the authority to revoke licenses of a broadcast station based on the content of a particular newscast."

Pai's response hasn't satisfied Democrats, who are criticizing the chairman for not going far enough in condemning Trump. But Gus Hurwitz, a visiting fellow at the American Enterprise Institute and assistant professor of law at the University of Nebraska College of Law, said Pai's approach was "exactly right," and deliberate.

"He didn't go out and make a direct statement on this," Hurwitz told the Washington Examiner. "He waited for a reporter to ask him a question, and his response was pretty bland. He said, ‘Look, we're the FCC. We're bound by the Constitution, and we're bound by statute, so we're not going to revoke a license based on a particular newscast.' "

Hurwitz said Pai wasn't stating his opinion about Trump's tweets, but rather made a factual statement about the FCC's authority, granted by statute.

But Hurwitz said the president's comments put Pai and the Republican commissioners in a bind.

"They are in a Catch 22 of sorts," he said. "This is really an overtly political issue. All of the commissioners at one point or another have a long history of support for the First Amendment, and a very serious unlikelihood of trying to pull a broadcast license for anything along these lines. The position that this has put them in is one where either they don't say anything, in which case it's a political firestorm, or they say something that is going to be in tension with concerns expressed by the president, in which case it's going to be a political firestorm.

"It's a lose-lose, and the reality of all the calls for them to say something is that it's political posturing where critics of the president are trying to create tension for the administration and the FCC," he continued.

Hurwitz said the FCC seldom revokes licenses, and said the best example of that rarity occurred when a California radio station had its license terminated after a woman died from water intoxication after competing in a contest called "Hold Your Wee for a Wii."

"There aren't many contemporary historical examples, but the best example is killing someone," Hurwitz said.

Still, Democratic lawmakers are clamoring for FCC commissioners to appear before at least two committees to weigh in on Trump's comments. An aide with the House Energy and Commerce Committee said all five commissioners are expected to attend a subcommittee hearing Wednesday.

Hurwitz predicted any appearance would be "exceptionally boring," as it's unlikely the Republican commissioners will stray far from what Pai said.

Plus, speaking out against Trump's threats could put the commissioners in a situation where they're forced to recuse themselves if the FCC is asked in the future to review a station's license, like a judge who expresses opinions about a case.

"The absolute worst-case scenario here would be that because of something that a commissioner said now, they were pressured or forced to recuse themselves when it mattered," Berin Szoka, president of TechFreedom, told the Washington Examiner.

If Pai or the other Republican FCC commissioners were to forcefully condemn Trump's tweets, Szoka warned there are ways Trump could retaliate.

The president could demote Pai, who was confirmed for another five-year term this month, to commissioner and name one of the other Republicans on the commission, Michael O'Rielly or Brendan Carr, chairman, he said. Or Trump could decide to replace O'Rielly when his term as commissioner ends in 2019 with someone allied closely with the president.

Once that new commissioner is confirmed, the president could then designate him or her chair.

"You have to start playing the question of who's in which seat, and when can they be replaced?" Szoka said. "If I were Ajit, I would be really careful about what I said now both to avoid having to recuse myself and to avoid getting into a fight with the president. The last thing you want is for the president to realize maybe he should replace Michael O'Rielly."

Still, replacing O'Rielly with a Trump loyalist in 2019 requires Senate confirmation, and the makeup of the Senate could change with the 2018 midterm elections.

Hurwitz says the president's tweets may have put the Republican commissioners in an awkward position over how to respond, but he believes Trump's comments were less about pressuring the FCC and Pai to act, and more about making a statement about the media.

"If you see the president say more directly, ‘It is time to revoke these licenses,' or, I can't imagine in a million years, but you see him actually have his lawyers or a surrogate file a petition requesting the revocation, until that happens, I think this is all political talk," he said, "and there's no expectation the commission will act behind it."