US government attempts to extradite a man accused of child sex crimes were blocked by the High Court on Thursday.
Two judges sitting in London allowed an appeal against extradition by fugitive Shawn Sullivan, 43, after the American authorities refused to give an assurance that he would not be placed on a controversial sex offenders treatment programme in Minnesota.
Sullivan has been described as one of the US's most-wanted alleged paedophiles, and has also been convicted of sexually assaulting two 12-year-old girls in Ireland.
His lawyers argued he could be declared "sexually dangerous" and placed on the US programme without a trial and with no hope of release.
Lord Justice Moses and Mr Justice Eady ruled on 20 June there was a real risk that, if extradited, Sullivan would be subjected to an order of civil commitment to the treatment programme in a "flagrant denial" of his human rights.
The judges then gave the US government a last opportunity to provide an assurance that there would be no commitment order made.
On Thursday Lord Justice Moses announced it had been confirmed by the Americans in a post-judgment note that "the United States will not provide an assurance", and Sullivan's appeal under the 2003 Extradition Act was therefore allowed.
"The appellant will be discharged from the proceedings," said the judge.
Sullivan, who has joint Irish-US nationality, is wanted to stand trial for allegedly abusing three American girls in the mid-1990s.
He was arrested in London in June 2010 while living with Ministry of Justice policy manager Sarah Smith, 34, in Barnes, south-west London.
They married while he was held at Wandsworth Prison, before he was granted bail.
His counsel Ben Brandon said at a one-day hearing in April that no one had been released from the treatment programme, operated by the Department of Human Services in Minnesota, since it began in its current form in 1988.
Commitment usually followed a person completing a prison sentence but a criminal conviction was not necessary for it to take place, said Mr Brandon.
Aaron Watkins, appearing for the US government, told the court Sullivan did not satisfy the criteria for civil commitment but agreed no assurances had been given.
The judges ruled there was a real risk Sullivan would face commitment and a flagrant denial of his right not to suffer loss of liberty without due process, a right protected by Article 5.1 of the European Convention on Human Rights.
Lord Justice Moses said under the programme "there is no requirement that the offences took place recently nor, indeed, that the misconduct resulted in conviction, provided that the misconduct is substantiated by credible evidence".
Mr Justice Eady said the risk of a flagrant denial of human rights was "more than fanciful".
He added: "That assessment of risk is borne out by the absence of any undertaking up to this point."
After giving the US government a final opportunity to offer an assurance, the judges allowed Sullivan's appeal against the home secretary's decision to extradite and district judge Howard Riddle's ruling at Westminster Magistrates' Court in December 2010 that there was no legal reason why he should not be removed.
Sullivan, who was not in court today, is accused of raping a 14-year-old girl and sexually molesting two 11-year-olds in Minnesota between 1993 and 1994.
He left the US as prosecutors filed charges against him and was later found to be living in Ireland. He then came to London using an Irish passport with his name spelt in Gaelic as "O'Suilleabhain".
While living in Ireland, he was convicted of sexually assaulting two 12-year-old girls and given a suspended sentence.