WikiLeaks founder Julian Assange received a legal win after the High Court in London allowed him to appeal his extradition to the United States. Last month, the court ruled Assange’s mental health was in appropriate shape for Assange to be extradited to the U.S., reversing a lower court ruling that said Assange was likely to kill himself if held under harsh U.S. prison conditions.

“What happened in court today is precisely what we wanted to happen,” Assange’s partner Stella Moris said Monday. “The High Court certified that we had raised a point of law of general public importance, and that the Supreme Court has good grounds to hear this appeal.”

Last month’s court ruling also said promises the U.S. had made were enough to guarantee Assange would be treated humanely within its criminal justice system. Monday’s ruling gave Assange permission to figure out “in what circumstances can an appellate court receive assurances from a requesting state … in extradition proceedings.” Supporters of Assange have questioned the authenticity of said assurances.

“Everybody that has looked into those so-called assurances have condemned them and judge them as not being worth the paper they are written on,” WikiLeaks editor-in-chief Kristinn Hrafnsson said Monday. “The American government has made such assurances before, and they have broken those assurances.”

The Assange extradition case will head to the U.K. Supreme Court. According to the court’s website, the court normally takes about two months after an application is submitted to decide whether to accept an appeal. If the court rejects Assange’s extradition appeal, he would be sent to the U.S. to face 17 charges of espionage and one charge of computer misuse. 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.

However, 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. On Monday, Hrafnsson called the U.S. case “a blatant and serious attack on press freedom worldwide.”