The lawyer for President Trump’s brother Robert says the president’s niece cannot publish a tell-all book about the the family because she is muzzled by a decades-old confidentiality agreement. In a statement on Saturday, Charles Harder, the infamous celebrity attorney, said that when the Trumps settled a legal dispute two decades ago, they signed an agreement not to publish books about their family relationships. This agreement, according to Harder, would prohibit Mary Trump from publishing her forthcoming book, Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man.

“Mary Trump reaped the rewards of the agreement for 20 years, and now seeks to breach the agreement by cashing in on a ‘tell-all’ book,” he said. “The enforcement of voluntary contracts is a pillar of our legal system. This private dispute has nothing to do with the First Amendment.” While an earlier court dismissed a motion to block the publication of the book, the Trump family on Friday refiled a request in a different court that could temporarily prevent publication. Simon & Schuster, the book’s publisher, did not immediately respond to a request for comment regarding Harder’s statement.

A person with knowledge of the matter told The Daily Beast regarding Harder’s statement, “There’s no precedent for enjoining a publisher in a situation like this.”

In a statement to The Daily Beast, Mary Trump’s attorney, Theodore Boutrous Jr., labelled Harder’s statement a “desperate attempt” by the Trump family to misuse NDAs to muzzle free speech. “The 20-year-old agreement now invoked by the President’s legal team is invalid and unenforceable for many reasons. The notion that seven members of the Trump family each mutually agreed to be gagged forever from speaking out about their ‘family relationships’ is absurd,” he said.

“If the agreement did that, then President Trump would have violated it when he recently proclaimed to Axios that he has a ‘good relationship’ with Mary Trump’s brother. That’s ridiculous, and so is this effort to use the courts to prevent publication of a book about the President in an election year. Courts repeatedly have rejected such efforts because a ban of a book is among the most dangerous and least tolerable violations of the First Amendment.”