Currently, the trust passes control of the company equally among Mr Murdoch’s four oldest children – Lachlan, James, Elisabeth and Prudence – after his death.
But Nevada commissioner Edmund Gorman rejected a bid to change the terms of the trust following a lengthy hearing.
Lachlan is head of Fox News parent Fox Corp and News Corp, which owns UK titles including The Sun and The Times.
Mr Murdoch’s proposed amendment would have blocked any interference by three of Lachlan’s siblings, who are more politically moderate.
Get set for more family infighting
This is a storyline which could be straight out of the TV drama Succession, which many already suspected was heavily based on the Murdoch family.
Rupert Murdoch, who is now 93, had been engaged in a lengthy court battle to try to hand over control of his media empire to his eldest son Lachlan when he dies.
Lachlan, who is more politically conservative than his siblings, would in theory consolidate the right-wing stance of some parts of Murdoch’s media empire – especially Fox News.
Today a document obtained by the New York Times revealed the commissioner in the case has whole-heartedly rejected the plan to change his trust, calling it a “bad faith” deal from Murdoch and his eldest son.
By bringing this case, Rupert Murdoch has made patently and painfully clear which of his children he favours.
There is some fascinating detail of art imitating life as the court heard how Mr Murdoch’s children had started secretly discussing a strategy for their father’s death.
They were prompted by an episode of Succession where media tycoon Logan Roy dies, throwing his family and empire into chaos.
The reality is that there will no doubt be more family infighting, as Rupert Murdoch’s lawyers say he is likely to appeal the judgment.
Mr Gorman said the plan to change the trust was a “carefully crafted charade”, according to The New York Times which first revealed details of the ruling.
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The newspaper also described that, in the commissioner’s opinion, it was an attempt to “permanently cement Lachlan Murdoch’s executive roles” inside the empire “regardless of the impacts such control would have over the companies or the beneficiaries” of the family trust.
Potentially, three of the heirs could out-vote a fourth, setting up a battle over the future of the companies.
“The effort was an attempt to stack the deck in Lachlan Murdoch’s favor after Rupert Murdoch’s passing so that his succession would be immutable”, the commissioner ruled.
“The play might have worked; but an evidentiary hearing, like a showdown in a game of poker, is where gamesmanship collides with the facts and at its conclusion, all the bluffs are called and the cards lie face up.”
A spokesman for Mr Murdoch could not immediately be reached for comment.
But his lawyer, Adam Streisand, said they were disappointed with the ruling and intended to appeal, The New York Times reported.
A spokesperson for Prudence, Elisabeth and James Murdoch said in an emailed statement to The Associated Press that they welcome the ruling and hope that their family can “move beyond this litigation to focus on strengthening and rebuilding relationships among all family members.”
Sky News, which Mr Murdoch launched in the UK in 1989, is no longer part of his empire.
At the end of 2018, Fox’s film entertainment assets, such as The Simpsons and the Avatar film franchise, were sold to Disney – while the company’s 39% stake in Sky was sold to Comcast.