The leader of the secret-spilling website is fighting extradition in part because Swedish rape trials are customarily held in secret, Geoffrey Robertson said at the start of a two-day extradition hearing. Closed-door hearings would be "a flagrant denial of justice ... blatantly unfair, not only by British standards but by European standards and indeed by international standards," he said.
The British lawyer representing Sweden, Clare Montgomery, countered that Swedish trials were based on the principle that everyone deserves "a fair and public hearing." She said that in cases where evidence is heard in private it will often be published after the trial and recited in the judgment.
Assange is accused of sexual misconduct by two women he met during a visit to Stockholm last year. Rape trials are often held behind closed doors in Sweden to protect the alleged victims.
He denies wrongdoing. Defense lawyers also argue he should not be extradited because he has not been charged with a crime, because of flaws in Swedish prosecutors' case -- and because a ticket to Sweden could eventually land him in Guantanamo Bay or on U.S. death row.
Montgomery, opened by dismissing several key planks of the defense. She said Marianne Ny, the Swedish prosecutor who is seeking Assange's extradition, did have the power to request the European Arrest Warrant, dismissing defense claims that she is not authorized to do so.
She said the rape allegation was an extraditable offense even under Sweden's broad definition of the crime. Assange's lawyers say he cannot be extradited because he has not been charged with a crime in Sweden and is only wanted for questioning -- and that the allegation is not rape as understood under European and English law.
Robertson said Assange faces an allegation known in Swedish as "minor rape."
"That is a contradiction in terms," he said. "Rape is not a minor offense." He said Assange had had consensual sex with his two accusers.
Montgomery contested this, saying "the Swedish offense of rape contains the core element of rape ... the deliberate violation of a woman's sexual integrity through penetration."
American officials are trying to build a criminal case against WikiLeaks, which has angered Washington by publishing a trove of leaked diplomatic cables and secret U.S. military files. Assange's lawyers claim the Swedish prosecution is linked to the leaks and politically motivated.
Preliminary defense arguments released by Assange's legal team claim "there is a real risk that, if extradited to Sweden, the U.S. will seek his extradition and/or illegal rendition to the USA, where there will be a real risk of him being detained at Guantanamo Bay or elsewhere."
Many legal experts say the Guantanamo claims are fanciful, and Sweden strongly denies coming under American pressure.
Nils Rekke, head of the legal department at the Swedish prosecutor's office in Stockholm, has said Assange would be protected from transfer to the U.S. by strict European rules.
"If Assange was handed over to Sweden in accordance with the European Arrest Warrant, Sweden cannot do as Sweden likes after that," he said. "If there were any questions of an extradition approach from the U.S., then Sweden would have to get an approval from the United Kingdom."
Assange, wearing a blue suit, was flanked by prison guards as the hearing opened at Belmarsh Magistrates' Court. Celebrity supporters including Jemima Khan and Bianca Jagger also attended.
WikiLeaks sparked an international uproar last year when it published a secret helicopter video showing a U.S. attack that killed two Reuters journalists in Baghdad. It went on to release hundreds of thousands of secret U.S. military files on the wars in Iraq and Afghanistan, and it later began publishing classified U.S. diplomatic cables whose revelations angered and embarrassed the U.S. and its allies.
The furor made Assange, 39, a global celebrity. The nomadic Australian was arrested in London in December after Sweden issued a warrant on rape and molestation accusations.
Released on bail on condition he live -- under curfew and electronically tagged -- at a supporter's country mansion in eastern England, Assange has managed to conduct multiple media interviews, sign a reported $1.5 million deal for a memoir, and pose for a magazine Christmas photo shoot dressed as Santa Claus.
The extradition case revolves around the contested events of Assange's trip to Sweden in August. Two Swedish women say they met Assange when he visited the country and separately had sex with him, initially by consent.
In police documents leaked on the Internet, one of the women told officers she woke up as Assange was having sex with her, but let him continue even though she knew he wasn't wearing a condom. Having sex with a sleeping person can be considered rape in Sweden.
Assange is also accused of sexual molestation and unlawful coercion against the second woman. The leaked documents show she accuses him of deliberately damaging a condom during consensual sex, which he denies.
Robertson denied Assange had committed any sexual offenses under English law. He said all relationships, long or short, contain "moments of frustration, irritation and argument. This doesn't mean, in this country, that the police are entitled to sniff under the bedclothes."
Assange's lawyers also complain they have not been given access to text messages and tweets by the two women which allegedly undermine their claims. They say text messages exchanged by the claimants "speak of revenge and of the opportunity to make lots of money."
The extradition hearing is due to end Tuesday, but Judge Howard Riddle could take several weeks to consider his ruling -- which can be appealed by either side.