If Steve Bannon signed a nondisclosure as part of his employment in the Trump campaign or in the White House, he very may well have violated it by talking to Michael Wolff for the new tell-all “Fire and Fury: Inside the Trump White House.”

But that doesn’t mean President Trump and his lawyer Charles Harder can do much about it, despite public threats this week, according to several leading labor law professors who spoke to VICE News.

First, any legal challenge of those agreements would open up Trump and the team to cross-examination under oath and discovery, which might be uncomfortable. “Litigating the details of those statements could be very embarrassing and might lead to disclosure in litigation of information that Trump would prefer not to disclose,” said Rip Verkerke, the director of employment and labor law studies at University of Virginia Law School.

Second, Bannon’s disclosures to Wolff are split between two very different circumstances: As a private employee during the campaign and as a public employee as chief strategist in the White House. While a nondisclosure agreement (NDA) might be enforceable when Bannon was working in the private sector, it wouldn't likely be for his work in the West Wing because of the First Amendment rights of public employees and statutes governing public service.

“The courts are likely to see this as an area of First Amendment interest,” said Samuel Estreicher, director of the Center for Labor and Employment Law and NYU Law School, making it difficult for Trump to prevail.

“I agree wholeheartedly that an absolute NDA (covering non-classified information) would likely be unenforceable if it covered the period during which an official serves with the government,” said Verkerke.

The NDA Bannon signed is not public, but it’s likely the same as or very similar to the NDAs signed by other senior staffers on the Trump campaign, which state:

“During the term of your service and at all times thereafter, you hereby promise and agree not to demean or disparage publicly the company, Mr. Trump, any Trump company, any family member, or any family member company.”

That language came from the NDA signed by former aide Sam Nunberg, who Trump accused in July of 2016 of violating his NDA. The case was settled out of court in August, the details of which are still unknown.

Public officials are usually legally allowed to speak out despite any agreements to keep information confidential. The case law is a bit unsettled, but the most relevant Supreme Court case is Snepp v. United States, involving a former CIA agent who published a book without first going through the agency’s approval process, thereby breaking a slightly different sort of confidentiality agreement. Even then, the Court allowed the book to be published and only allowed the government to seize the author’s royalties.

The NDA covering Bannon’s three months on the Trump campaign, however, is more complicated.

A campaign is technically a private entity, and an NDA would apply to it. It’s why many members of Hillary Clinton’s campaign also had to sign NDAs.

Labor law experts say that Trump has a better chance of winning his case here but that the outcome is not at all certain. Plus, the process of trying to sue Bannon would require the president to undergo discovery under oath and could be extremely damaging politically. Even if he somehow wins, he would still lose, they say.

“It’s not that easy to enforce an NDA,” said Estreicher, adding that “if public figures like President Trump or his children try to use reach of contract law in this manner, the courts are likely to push back as they have on defamation and libel.”

It's become harder and harder to win defamation and libel cases in court over the past three decades as courts have erred on the side of free speech. Usually, a plaintiff must prove that someone made claims “with knowledge that it was false or with reckless disregard of whether it was false or not,” a high legal bar.

Some labor experts also suggested that the NDA would not be enforceable now that the campaign is over for more than a year.

“It’s enforceable only if reasonable in scope and duration,” said Alan Hyde, a professor at Rutgers Law School. “An NDA during a campaign is probably reasonable, but it becomes unreasonable once the campaign ends.”