Rosengart stepping down comes as all litigation pertaining to Spears' former conservatorship has been resolved, reinstating the pop star's independence and releasing her from the probate system.
Two months ago, under Rosengart's representation, Spears reached a settlement with her estranged father, avoiding a potentially heated trial and concluding their contentious dispute over legal fees that had persisted beyond the termination of her conservatorship in November 2021.
With the settlement reached and all other loose ends tied to Spears' litigation finalized, Rosengart, who is a Los Angeles-based partner at the firm Greenberg Traurig, is moving on to focus on his heavy caseload for other clients, the source said.
At the time of the settlement, Rosengart told CNN, "It has been our honor and privilege to represent, protect, and defend Britney Spears," calling her an "icon and a brilliant and brave artist of historic and epic proportion."
Rosengart did not respond to CNN's request for comment regarding the end of his working relationship with Spears.
Spears hired Rosengart - a former federal prosecutor - in the summer of 2021, after she had been working with a court-appointed attorney for the majority of her conservatorship, which she was placed under in 2008.
Rosengart emerged as a key figure in Spears' effort to end her conservatorship. She has frequently credited him with protecting her and restoring her civil liberties. Spears' father, Jamie Spears, served as the singer's conservator for most of its 13-year duration, overseeing his adult daughter's finances and medical decisions.
In June 2021, Spears gave explosive testimony in court, pleading with the judge to break her free from the conservatorship, which she said was "abusive."
"I just want my life back. It's been 13 years and it's enough," Spears told the judge, claiming that she was forced by her management and father to go on tour against her will, could not drink coffee, was put on lithium that made her feel "drunk" and was not allowed to get married or have a baby as she wished.
In July 2021, Spears testified again, making a tearful plea to the judge to remove her father from her conservatorship, which led to the court's decision to grant Spears her own attorney. She retained Rosengart to litigate her case.
Within two months of working with Rosengart, the court suspended Spears' father as her conservator, and then ultimately terminated the conservatorship less than two months later.
Rosengart - who has also represented Hollywood figures including Sean Penn and Steven Spielberg in legal matters - was hailed as a hero by legions of #FreeBritney supporters, becoming a significant figure throughout the legal saga. As Spears' case captivated the world, the attorney was the frequent subject of memes and viral posts across social media, dubbed by some fans as "RosenGod."
Spears and Rosengart have a close connection that is atypical from standard attorney-client relationships.
When Rosengart was hired in July 2021, Spears posted to her Instagram: "Now with real representation today ... I feel GRATITUDE and BLESSED !!!!" In February 2022, the star shared a photo of the two in matching pink outfits, writing, "This man has turned my life around."
In Spears' memoir, "The Woman in Me," which was published last year, she wrote that Rosengart's legal strategy led her to court victory. "He told me that I deserved the credit for what happened," Spears wrote in the book.
Since her conservatorship was terminated, Spears published her memoir and has released two singles, "Hold Me Closer" with Elton John and "Mind Your Business" with will.i.am. She also got married and divorced to fitness trainer and actor Sam Asghari.
Throughout Spears' legal battle, many accusations were made against her father in legal filings pertaining to financial misuse and abusing his role as conservator. The elder Spears has always maintained there was no wrongdoing on his part, stating that the court approved every step of the conservatorship. When Spears reached a settlement with her father this past April, his attorney, Alex Weingarten, told CNN that he "would have liked to have had a trial so that the truth came out."
"Jamie would love nothing more than to disclose all of the details and has nothing to hide, but that is not the situation unfortunately," Spears' father's attorney said, adding that he "loves his daughter very much and worked tirelessly to protect her."
But Spears wanted to bring her long-running legal battle to a close.
"As she desired, her freedom now includes that she will no longer need to attend or be involved with court in this matter," Rosengart told CNN, in April.
"Although the conservatorship was terminated in November 2021, her wish for freedom is now truly complete," he said.
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