A judge on Tuesday issued a temporary restraining order blocking publication of a tell-all book by Donald Trump’s niece.
Mary Trump’s book was set to be released on July 28 and she has promised to lift the lid on family feuds.
Robert Trump, the president’s younger brother, sued to prevent it from coming out.
Judge Hal Greenwald of Dutchess County Supreme Court in New York said he was temporarily stopping publication while arguments were considered. His order lasts until the conclusion of the case.
He asked lawyers for Mary Trump, and the publisher Simon & Schuster, to appear in court on July 10.
A previous attempt by Robert Trump to block the book was dismissed in a different New York court last week.
Ted Boutrous, Mary Trump’s lawyer, said the latest order was a violation of the First Amendment, which protects free speech, and would be appealed.
Mr Boutrous said: “The trial court’s temporary restraining order is only temporary but it still is a prior restraint on core political speech that flatly violates the First Amendment.
“We will immediately appeal. This book, which addresses matters of great public concern and importance about a sitting president in election year, should not be suppressed even for one day.”
According to the publisher the book “shines a bright light on the dark history of their family in order to explain how her uncle became the man who now threatens the world’s health, economic security, and social fabric.”
The president has said that Mary Trump is “not allowed” to publish the book because she signed a nondisclosure agreement.
Her book is called “Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man”.
Mary Trump is the daughter of Donald Trump’s elder brother Fred Trump Jr, who died in 1981.
Charles Harder, Robert Trump’s lawyer, said his client was “very pleased” with the order.
Mr Harder said: “We look forward to vigorously litigating this case, and will seek the maximum remedies available by law for the enormous damages caused by Mary Trump’s breach of contract, and Simon & Schuster’s intentional interference with that contract.”
He added: “Short of corrective action to immediately cease their egregious conduct, we will pursue this case to the very end.”