Judge Howard Riddle decided that the allegations of rape and molestation by two Swedish women are extraditable offenses and that a Swedish warrant was correctly issued, The Associated Press reported.
Assange has seven days to appeal the decision, a process that could mean the case could drag on until the summer. His lawyers said they will definitely appeal.
According to the AP, Assange's Swedish lawyer, Bjorn Hurtig, is already preparing to represent his client.
"If he comes to Sweden, I think he has great chances of being freed," Hurtig said. "And I'll be waiting for him, ready to fight for him tooth and nail."
Claes Borgstrom, the lawyer representing the two women, was not surprised by the decision, according to the AP.
"It's just too bad that it took so long," Borgstrom said. Assange "will probably appeal this decision for some reason that is hard to understand. He claims that he hasn't committed a crime, so he should just come here and sort it out. I expect that he will be on Swedish soil before the summer."
Assange's legal team has argued that if the 39-year-old Australian is extradited to Sweden, he could in turn be extradited to the U.S., where federal officials reportedly want to prosecute him under the Espionage Act because of WikiLeaks' release of thousands of classified documents and diplomatic cables. The website's activities are under investigation in the U.S., The Guardian reported today.
Assange's lawyers say he could face the death penalty if found guilty of espionage charges, or be imprisoned at Guantanamo Bay. But for Assange to be extradited from Sweden, officials there would have to ask permission from Britain for the extradition.
Assange's lawyers also say Assange will not receive a fair trial in Sweden. Riddle specifically disagreed with that today.
The allegations, which eventually led to an Interpol red notice warrant for Assange's arrest in late November, involve a 10-day period after he arrived in Sweden Aug. 11 to give a seminar lecture.
Assange admits having consensual sexual relationships with both women but denies there was any coercion or violence involved.
He has been under a type of house arrest at a friend's country mansion in Norfolk, England, under strict conditions that require him to wear an electronic ankle tag and report to police daily.