Infuriating politicians, the Court of Appeal said it was not relevant that terror suspect Abu Qatada was regarded as "extremely dangerous".
Abu Qatada has been described as "a truly dangerous individual", using human rights, he has made a series of challenges against deportation.
Abu Qatada will remain in custody following his arrest for allegedly breaking his bail conditions, a judge ruled.
The Home Office today said it will now request permission to appeal against the decision to allow Abu Qatada to remain in the UK directly from the Supreme Court.
The Home Office asked the Court of Appeal today for permission to appeal to the Supreme Court over its recent decision to allow hate preacher Abu Qatada to stay in the UK
After a decade of legal wrangling an appeal court decision has made it all but impossible for the government to deport Abu Qatada. The three judges ruled there is a "real risk of a flagrant denial of justice" if the radical cleric has to stand trial in Jordan on terror charges.
The Home Office insists the legal battle isn't over. Juliet Bremner reports from the Royal Courts of Justice.
– Yvette Cooper, Shadow home secretary
This is an extremely serious and disappointing judgment which rips apart Theresa May's strategy for deporting Abu Qatada and contradicts her repeated assurances to Parliament that her approach would get him swiftly on to a plane.
According to security experts, the Home Secretary and the courts, this is an extremely dangerous man, and we all want him to be deported to stand fair trial abroad as soon as possible and to be held in custody in the meantime.
Appeal Judges upheld a decision made in November by the Special Immigration Appeals Commission (SIAC):
SIAC was entitled to conclude that there is a real risk that the impugned statements will be admitted in evidence at a retrial and that, in consequence, there is a real risk of a flagrant denial of justice.
Lord Dyson, Lord Justice Richards and Lord Justice Elias said the court accepted that Qatada "is regarded as a very dangerous person", but that was not "a relevant consideration" under human rights laws.
There's a strong possibility now that the Home Secretary may try for a conviction for Abu Qatada in the British courts.
The Home Office says it will to seek leave to appeal, adding:
"This is not the end of the road, and the Government remains determined to deport Abu Qatada. We will consider this judgment carefully and plan to seek leave to appeal. In the meantime we continue to work with the Jordanians to address the outstanding legal issues preventing deportation."
- The Home Secretary's legal team argued Abu Qatada was a "truly dangerous" individual who escaped deportation through "errors of law"
- The Special Immigration Appeals Commission decided in November that Qatada could not be removed to Jordan without "a real risk" of evidence obtained through torture being used against him at a retrial
- Today Lord Dyson, the Master of the Rolls, and two other judges unanimously rejected the appeal
Home Secretary Theresa May has lost her challenge in the appeal court over a decision allowing radical preacher Abu Qatada to stay in the UK.