The arbitrator, T. Andrew Brown, said in the ruling that the terms of the nondisclosure agreement were "highly problematic" because it did not adhere to typical legal standards, describing it as "vague, indefinite, and therefore void and unenforceable."
"The Agreement effectively imposes on [Manigault Newman] an obligation to never say anything remotely critical of Mr. Trump, his family or his or his family members' businesses for the rest of her life," Brown said in the ruling.
Manigault Newman and her attorney released statements celebrating the decision Tuesday.
"Clearly, I am very happy with this ruling," Manigault Newman said. "Donald has used this type of vexatious litigation to intimidate, harass and bully for years! Finally the bully has met his match!"
Her attorney, John Phillips, said in his statement that he hopes the ruling encourages more people to "come forward and blow the whistle on corrupt government."
"It's over. We've won in Donald Trump and the Trump Campaign's chosen forum," he said.
Trump's campaign filed an arbitration complaint against Manigault Newman with the American Arbitration Association in New York City in 2018, alleging that she was in breach of a 2016 confidentiality agreement.
The action was related to claims Manigault Newman made in her 2018 book, "Unhinged: An Insider's Account of the Trump White House," in which she called Trump a racist and suggested that he was in severe mental decline.
Trump hosted the reality television show "The Apprentice" and its spinoff, "The Celebrity Apprentice," both of which aired on NBC, from 2004 to 2015 before he ran for president. "The Celebrity Apprentice" was produced and owned by MGM.
Newman was a three-time contestant on the show and over time became a close confidant of Trump before she supported him for president and followed him to the White House. During his campaign, she was one of his most prominent Black supporters. However, their relationship soured during her time in the administration, and she was reported to have been forced out in 2017. Manigault Newman has insisted that she left on her own terms.
In her book, Manigault Newman wrote that she had not signed a nondisclosure agreement for her work in the White House. She asserted in the book that within 24 hours of her departure, Lara Trump, the president's daughter-in-law, emailed her a contract to work on Trump's re-election campaign for $15,000 per month in exchange for signing a nondisclosure agreement that was "as harsh and restrictive as any I'd seen in all my years of television."
Brown, the arbitrator, said that given how vaguely the agreement was written, there would be no way for Manigault Newman to know whether she was in breach of the contract.
"The statements do not disclose hard data such as internal polling results or donor financial information," Brown wrote. "Rather, they are for the most part simply expressions of unflattering opinions, which are deemed 'confidential information' based solely upon the designation of Mr. Trump. This is exactly the kind of indefiniteness which New York courts do not allow to form the terms of a binding contract."
Brown said Trump's campaign would have to pay Manigault Newman's legal fees.