LONDON (AP) -- WikiLeaks founder Julian Assange on Monday won the first stage of his effort to overturn a U.K. ruling that opened the door for his extradition to U.S. to stand trial on espionage charges.
The High Court in London gave Assange permission to appeal the case to the U.K. Supreme Court. But the Supreme Court must agree to accept the case before it can move forward.
"Make no mistake, we won today in court," Assange's fiancee, Stella Moris, said outside the courthouse, noting that he remains in custody at Belmarsh Prison in London.
"We will fight this until Julian is free," she added.
The Supreme Court normally takes about eight sitting weeks after an application is submitted to decide whether to accept an appeal, the court says on its website.
The decision is the latest step in Assange's long battle to avoid a trial in the U.S. on a series of charges related to WikiLeaks' publication of classified documents more than a decade ago.
Just over a year ago, a district court judge in London rejected a U.S. extradition request on the grounds that Assange was likely to kill himself if held under harsh U.S. prison conditions. U.S. authorities later provided assurances that the WikiLeaks founder wouldn't face the severe treatment his lawyers said would put his physical and mental health at risk.
The High Court last month overturned the lower court's decision, saying that the U.S. promises were enough to guarantee Assange would be treated humanely.
Those assurances were the focus of Monday's ruling by the High Court.
Assange's lawyers are seeking to appeal because the U.S. offered its assurances after the lower court made its ruling. But the High Court overturned the lower court ruling, saying that the judge should have given the U.S. the opportunity to offer the assurances before she made her final ruling.
The High Court gave Assange permission to appeal so the Supreme Court can decide "in what circumstances can an appellate court receive assurances from a requesting state ... in extradition proceedings."
Assange's lawyers have argued that the U.S. government's pledge that Assange won't be subjected to extreme conditions is meaningless because it's conditional and could be changed at the discretion of American authorities.
The U.S. has asked British authorities to extradite Assange so he can stand trial on 17 charges of espionage and one charge of computer misuse linked to WikiLeaks' publication of thousands of leaked military and diplomatic documents.
Assange, 50, has been held at the high-security Belmarsh Prison since 2019, when he was arrested for skipping bail during a separate legal battle. Before that, he spent seven years holed up inside Ecuador's Embassy in London. Assange sought protection in the embassy in 2012 to avoid extradition to Sweden to face allegations of rape and sexual assault.
Sweden dropped the sex crimes investigations in November 2019 because so much time had elapsed.
American prosecutors say Assange unlawfully helped U.S. Army intelligence analyst Chelsea Manning steal classified diplomatic cables and military files that WikiLeaks later published, putting lives at risk.
Lawyers for Assange argue that their client shouldn't have been charged because he was acting as a journalist and is protected by the First Amendment of the U.S. Constitution that guarantees freedom of the press. They say the documents he published exposed U.S. military wrongdoing in Iraq and Afghanistan.