Their ruling in the case of Paul Bennett, a New Zealander who alleges the British authorities connived in his illegal kidnapping and expulsion from South Africa, plugs a loophole in extradition law.
Previous court decisions have tended to suggest that if a person was arrested and charged properly on arrival in the United Kingdom, it did not matter whether or not the law was broken in bringing him or her here.
But yesterday the judges said that courts should accept a responsibility 'to refuse to countenance behaviour that threatens either basic human rights or the rule of law'.
Mr Bennett says he was detained by South African police at the behest of Scotland Yard, held for three-and-a-half weeks and moved to London in defiance of a South African Supreme Court order. He also claims British diplomats in South Africa gave him a false UK passport. The Crown Prosecution Services had also decided not to pursue extradition in connection with allegations of obtaining finance for a helicopter by deception.
Although there are known to be a handful of prisoners in British jails, including one man convicted of IRA offences, who claim to have been kidnapped abroad, Lord Lowry said the ruling should not open floodgates. 'If British officialdom at any level has participated in or encouraged the kidnapping, it seems to represent a grave contravention of international law, the comity of nations and the rule of law generally if our courts allow themselves to be used by the executive to try an offence which the courts would not be dealing with if the law of rule had prevailed.'
Mr Bennett, who has now spent two-and-a-half years in jail in England without trial, said he was delighted with the ruling and hoped the charges against him - which he has always contested - would now be dropped.