Earlier in 2026, siblings Edward, Dominic, Marie-Nicole and Aldo Cascio sued the late King of Pop's estate after alleging the Thriller hitmaker - who died in 2009 aged 50 - "groomed and brainwashed" them when they were minors.
But on Wednesday, Judge Hernán D Vera ruled the matter needs to be handled in confidential arbitration under the clear terms of a 2019 settlement between the quartet and the estate.
In documents obtained by Billboard, the judge wrote: "Although the allegations are horrific, the court is without discretion to do aught but enforce the language of the arbitration clause."
The siblings - who grew up with Jackson and once referred to themselves as his "second family" - had previously been staunch supporters of the singer but in 2019, following the release of shocking documentary Leaving Neverland, they first made allegations against the late star and reportedly claimed privately at the time they had been "deprogrammed" as a result of the film.
Although there was no admission of wrongdoing, the estate paid them a $A6.7 million settlement, which the Cascios later argued is void and unenforceable because they were coerced into signing the agreement.
But the judge noted their arguments, "while serious", do not belong in a public courtroom because of the settlement.
He wrote: "While plaintiffs are fully within their rights to raise questions about unconscionability, those challenges must be presented later before an arbitrator."
The ruling echoed a similar decision made in March by a different judge in California, who oversaw legal proceedings relating to fifth brother Frank Cascio's sexual assault claims.
In that case, the judge ruled arbitration was required for all future disputes because Frank had signed the same settlement agreement.
The Cascios lawyer branded the latest ruling "disappointing but not surprising".
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