Australian Julian Assange, founder of the anti-secrecy Web site WikiLeaks, yesterday lost a UK Supreme Court appeal that sought to block his extradition to Sweden to face “rape” claims brought by a Swedish prosecutor.

The court, in a 5-2 vote, rejected Assange’s argument that the Swedish prosecutor who investigated the sexual assault claims and issued a European arrest warrant for him in 2010 wasn’t a “judicial authority” under European Union law.

Assange’s lawyer Dinah Rose said she may seek to re-open the matter by challenging the court’s handling of the case. Assange may also appeal to the European Court of Human Rights.

Assange is accused of failing to use a condom with one of two Swedish women with whom he spent the night and in the morning having sex with the other while she was asleep, both of which can amount to “rape” under Swedish law. He claims the sex was consensual.

His backers are concerned that the Swedish case is being brought to bring him outside the UK justice system, and possibly open the way for American authorities to seek his extradition to the US to face charges over his publication of secret documents, which would carry far more serious penalties.

However that would almost certainly bring behind-the-scenes pressure from the Gillard Government in Australia. Bob Carr is presumably reading up on it right now.