In December, the High Court overturned a lower court’s ruling that Assange should not be extradited because his mental health problems meant he would be at risk of suicide.
While judges on Monday refused him permission for a direct appeal to the Supreme Court on their decision, they said his case raised an issue of legal importance that he could ask the UK’s top court to rule on.
This means the Supreme Court will have to decide whether or not it should hear his challenge. The ruling will stall any extradition from the UK for now.
US officials accuse Assange of 18 offenses – 17 counts of espionage and one of computer misuse – relating to WikiLeaks’ release of confidential US military records and diplomatic cables about 10 years ago.