Speaking to a packed courtroom in southeast London, Judge Howard Riddle said Swedish prosecutors' request that Assange be forced to return to Stockholm was issued properly and would not infringe on his human rights.
"I must order that Mr. Assange be extradited to Sweden," Riddle said at the conclusion of his 28-page judgment, which he read aloud while Assange, in a dark suit and tie, looked on impassively from the witness dock.
Swedish authorities want to question the 39-year-old Australian over allegations of sexual molestation, unlawful coercion and rape made in August by two Swedish women - accusations that Assange denies.
One of the women, known in court as Miss A, says that Assange initially had consensual sex with her but that it became nonconsensual after a condom broke. The other, known as Miss B, says that Assange had unwanted, unprotected sex with her while she was asleep, an act punishable in Sweden by up to four years in jail.
Assange rocked the world of international diplomacy last year when his whistleblowing Web site released thousands of secret U.S. government cables. Assange's legal team says that the allegations against him are politically motivated and that if sent to Sweden, he would be at risk of extradition to the United States.
Speaking to a sea of reporters outside Belmarsh Magistrates' Court, a defiant Assange said the ruling was a "result of a European arrest warrant system run amok" and vowed to appeal.
In court Thursday, Riddle dismissed all of the defense's arguments, point by point, including the assertion that Assange's actions would not qualify as rape in Britain and did not, therefore, constitute an extraditable offense. Of Miss B's allegations, the judge said: "In this country that would amount to rape."
He also said that Marianne Ny, the Swedish prosecutor seeking Assange's arrest, was within her rights to issue a European arrest warrant and rejected assertions that Assange would not get a fair trial in Stockholm because of the Swedish practice of hearing rape cases partially behind closed doors.
He added that Assange's Swedish attorney, Bjorn Hurtig, had "fatally undermined" the defense when he made a mistake on the basic fact of when Ny had first requested an interview with Assange.
And although Riddle acknowledged that there had been a spate of "adverse publicity" about Assange in Sweden, including remarks by the Swedish prime minister, he rejected the assertion that this would prejudice a trial.
Assange's legal team has seven days to lodge an appeal with London's High Court. Extradition experts predict that the case could drag on for several months, given the various avenues available for appeal.
The judge also upheld Assange's current bail conditions - wearing an electronic tag, residing at a supporter's country estate and checking in nightly with police - which Assange called extreme under the circumstances.
"Why is it that I am subject, a nonprofit free-speech activist, to a $360,000 bail?" he said to reporters outside the court. "Why is it that I am kept under electronic house arrest when I have not even been charged in any country?"