A British appellate court Friday overturned a lower court’s decision that WikiLeaks founder Julian Assange’s mental health was too fragile to withstand the US criminal justice system, potentially paving the way for his extradition to face charges under the Espionage Act for publishing classified military and diplomatic cables. The High Court in London ruled that US assurances were enough to address concerns regarding Assange’s treatment and directed a lower court judge to send the extradition request to Britain’s interior minister for review. Home Secretary Priti Patel, who oversees law enforcement in the UK, will make the final decision on whether to extradite Assange.

“There is no reason why this court should not accept the assurances as meaning what they say,” the High Court ruling stated. “There is no basis for assuming that the USA has not given the assurances in good faith.”

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Assange’s fiancé, Stella Moris, called the decision a “grave miscarriage of justice” and said Assange’s lawyers would seek to appeal to the UK Supreme Court.

“We will fight,” Moris said outside court, where supporters gathered with banners demanding Assange’s release.

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“Every generation has an epic fight to fight and this is ours, because Julian represents the fundamentals of what it means to live in a free society,” she said.

The 50-year-old Australian is currently being held at London’s high-security Belmarsh Prison. The High Court ordered that Assange remain in custody pending the outcome of the extradition case.

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In January, District Judge Vanessa Baraitser refused the US request to extradite Assange on health grounds, saying the Australian citizen was likely to kill himself under harsh prison conditions.

James Lewis, a lawyer for the US government, had said at the time Assange “has no history of serious and enduring mental illness.” 

US authorities have told British judges that if Assange is extradited for prosecution, he would be eligible to serve any US prison sentence he receives in his native Australia. The authorities also said he wouldn’t be held at the supermax penitentiary in Florence, Colorado, the highest-security prison in the United States.

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Assange has been indicted on 17 espionage charges and one charge of computer misuse over WikiLeaks’ publication of thousands of leaked military and diplomatic documents. The charges carry a maximum sentence of 175 years in prison, although Lewis said “the longest sentence ever imposed for this offense is 63 months.”