Scheinkman left in place a restraint that blocked Mary Trump and any agent of hers from distributing the book, but the court made clear it was not considering the publisher to be an agent, though that issue could be decided in further proceedings at the lower court.
"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", said Mary Trump's lawyer, Theodore Boutrous.
Thousands of copies of President Donald Trump's niece's book "Too Much and Never Enough: How My Family Created the World's Most Dangerous Man" have already been shipped out, according to publisher Simon & Schuster. Robert Trump then filed his petition with the state's Supreme Court.
The ruling issued Wednesday allows publisher Simon & Schuster to print and distribute the 240-page book by Mary Trump, who dubs the United States president "the world's most unsafe man". Simon & Schuster claim that the injunction violates their First Amendment rights by "restrain [ing] speech on a matter of public interest".
Mary's attorney vowed to immediately appeal.
In the book, Mary, a clinical psychologist, recounts what she witnessed of the "toxic family" in the home of her grandparents, according to her publisher.
This is an appeal from an order prohibiting Simon & Schuster, Inc.
Their settlement almost two decades ago included a confidentiality clause that explicitly states they would not "publish any account concerning the litigation or their relationship", unless all of them agreed, according to court papers. A July 10 hearing is scheduled.
The restraining order was requested by President Donald Trump's brother, Robert Trump, who said that the book would violate a nondisclosure agreement that was part of the estate of President Trump's father, Fred Trump, after his death in 1999.
"She explains how specific events and general family patterns created the damaged man who now occupies the Oval Office, including the unusual and harmful relationship between Fred Trump and his two oldest sons, Fred Jr. and Donald", according to the book's description.
In a statement from Mary Trump's lawyer, Mr Boutrous said: "President Trump and his siblings are seeking to suppress a book that will discuss matters of utmost public importance".
Adam Rothberg, a Simon & Schuster spokesperson, said the publisher was disappointed but looks forward "to prevailing in this case based on well-established precedents regarding prior restraint".
He also said, however, that the 20-year-old agreement to protect the Trump family's privacy may have been altered by the fact that Donald Trump had become the president during that time.
Robert Trump has argued that as part of litigation related to Fred Trump's will, a settlement was reached that included a confidentiality provision. She and her brother Fred III said in court papers that someone in or connected to the Trump family got Fred Sr.to change his will and give them less than they expected.
Charles Harder, an attorney for Robert Trump, said his client was "very pleased".