But Trump’s double-barreled response is risky, both as a matter of law and as a matter of politics.

“It would surely be another terribly self-destructive act by the president if some sort of action were commenced on his behalf,” the First Amendment lawyer Floyd Abrams told me Thursday. “The chances of success in such an action are all but nonexistent and the risks to the president of commencing such an action are overwhelming.”

A suit against Wolff and his publisher would be especially tough. In order to win, Trump would likely have to prove that Wolff and the publisher printed information that they knew was false. In the United States, it’s very hard to win a libel suit against a publisher or media outlet—as Trump knows well, since he has repeatedly complained that libel laws need to be loosened for plaintiffs. Many of the most damaging quotes to emerge from the book so far, like Bannon’s description of the June 2016 Trump campaign meeting with a Russian lawyer as “treasonous,” or aides’ repeated assessments of the president as unintelligent and distracted, are matters of opinion and not fact, and therefore not subject to libel laws.

Besides, the book is already printed and shipped. There’s no real way to stop it reaching the public at this point; the first quotes emerged when The Guardian found a copy at a bookstore ahead of the release date.

The open question is what sort of confidentiality or non-disparagement agreements Bannon might have signed. While Abrams said such contracts wouldn’t likely affect Wolff’s right to report what Bannon told him, it could open Bannon up to lawsuits.

Trump is a longtime aficionado of NDAs, and many former campaign staffers seem to have signed them, including former manager Corey Lewandowski and aide Sam Nunberg, whose NDA was entered into the record as part of a lawsuit Trump filed against Nunberg for leaking. Trump might have a case against Bannon for anything Bannon said about Trump before he was president, but Abrams doubted there’d be any enforceable equivalent that applied to Bannon’s work in the White House. “Once Bannon was in the government I think it highly unlikely that anything he said could be the basis of a contractual lawsuit by the president,” he said.

NDAs often serve largely as a deterrent. When Lewandowski joined CNN as a commentator, legal experts told The Washington Post that it might be tough to enforce his NDA, but that threat of defending a costly lawsuit for people who break such a contract tends to keep them from doing so. If they do violate the deal, though, the damage is done, and a lawsuit can be punitive but never restorative.

There are, however, considerable risks for Trump in filing suit. Some observers have claimed the simple fact of a lawsuit would validate the book. “The White House can’t argue simultaneously that the book is completely incorrect and Bannon violated a non-disclosure agreement,” Politico’s Playbook argued. “If he violated a non-disclosure agreement then something he said was right!” But Abrams said that argument, while not ridiculous, was overblown. For example, Trump made his ex-wife Ivana sign an agreement in which she agreed not to say anything about him—positive, negative, or neutral. It’s conceivable (if hard to believe) that Bannon could have signed a similar agreement.