On Thursday, a lawyer working for President Donald Trump sent a cease-and-desist letter to journalist Michael Wolff. Wolff had just released excerpts from his new book, Fire and Fury, depicting the Trump administration as a chaotic swirl of incompetence and exploitation, and Trump’s lawyer threatened a libel suit if Wolff and his publisher, Henry Holt and Co., did not stop distribution of the book immediately.

The president has alleged on Twitter that Wolff’s book is “phony” and “full of lies, misrepresentations and sources that don’t exist.” But the letter from Trump’s counsel seems to have been fairly counterproductive — in response, Henry Holt and Co. simply moved up Fire and Fury’s publication date from January 9 to January 5 and basked in all the press coverage.

Regardless, the letter has given the Authors Guild cause for concern.

The Authors Guild is a legal advocacy group for authors whose mission is to protect them from predatory contracts and lawsuits, among other things. In a statement released Thursday night, the guild declared itself “dismayed” by Trump’s “unprecedented” attack on Wolff’s book.

“To the Guild’s knowledge, no prior President has sued a writer for libel, and for good reason,” reads the statement. (Per the New York Times, Jimmy Carter once threatened to sue the Washington Post for libel after it alleged that he’d bugged Nancy and Ronald Reagan, but he dropped the threat after the paper issued a retraction.) “The ability to criticize the government and its leaders lies at the essence of the First Amendment’s protection of free speech; and threats of libel lawsuits are one of the de facto primary means of curtailing free speech in this country today.”

The statement also includes a quote from Authors Guild president James Gleick. “This isn’t a country where we quash books that the leader finds unpleasant,” Gleick said. “That’s what tyrants do, not American presidents.”

The accuracy of Wolff’s reporting has been disputed by people besides Trump. In 2004, New Republic journalist Michelle Cottle wrote that “the scenes in his columns aren’t recreated so much as created — springing from Wolff’s imagination rather than from actual knowledge of events.” And as Vox’s Andrew Prokop explained, some of Wolff’s sourcing for the events of Fire and Fury is either hazy or dubious, and a few details he’s reported seem to contradict known facts. (For instance, it’s unlikely that Trump did not know who John Boehner was in January 2017, as Wolff reports, given that Trump had mentioned him on Twitter multiple times before then.)

But Trump’s cease-and-desist letter does not point to any specific facts as untrue or libelous, and Trump has a history of wielding the threat of libel suits as a cudgel to silence anyone who says something about him that he does not like, regardless of its accuracy. He threatened to sue Rosie O’Donnell for libel when she said that he’d declared bankruptcy (he had, which is perhaps why he apparently never filed the suit), and he spent five years suing writer Timothy O’Brien after O’Brien wrote that Trump’s net worth was lower than Trump claimed. (Trump lost.)

The full statement from the Authors Guild is available online here.