In a decision by the High Court in Auckland, Judge Toogood dismissed an appeal against the extradition order.
The judge laid out a timeline of events, detailing the "inexplicable and inexcusable" periods of inaction between the UK and New Zealand authorities.
"Mr Keenan's sense of grievance that such a lengthy period has expired before the authorities finally apprehended him in this country is understandable," the judge said.
"There is considerable force, however, in the respondent's submissions that Mr Keenan brought these consequences upon himself by failing to appear at his trial in May 2003."
Judge Toogood said by the time UK authorities confirmed Keenan was in New Zealand, they had "mislaid the original [arrest] warrant", so their first extradition request was incomplete.
"There were lengthy bureaucratic delays," the judge said.
"Twice, New Zealand's Ministry of Foreign Affairs and Trade sought revised extradition requests which would meet New Zealand requirements."
It was not until June 2014 that a new arrest warrant was issued for Keenan, and a third extradition request was sent last year, based on the new warrant. The original of the new warrant was not sent to New Zealand until half way through last year.
During the time the authorities were working on extradition requests, Keenan obtained New Zealand citizenship and a New Zealand passport, changed his name to Alan Mackenzie MacDonald, and visited his mother in the UK, taking a ferry from Ireland to avoid having to show his passport to UK authorities.
Following the successfully laid extradition order, Keenan appealed, on the grounds the warrant was invalid, the District Court judge erred in accepting evidence around the validity of the warrant, and the judge erred in her consideration of time delays.
Judge Toogood dismissed the appeal and ordered Keenan to report to the Auckland Central Police Station by Monday and to cooperate with authorities in his extradition.
A Department of Internal Affairs spokesman said they were would be "looking into how this individual obtained citizenship and considering if any further action is required".
He would not comment on whether a person facing sexual charges would normally be excluded from obtaining citizenship, or under which circumstances, if any, they would be granted citizenship.