The US Supreme Court has thrown out an appeal by a Lebanese-born German citizen who accuses the CIA of kidnapping and torturing him.
Khaled al-Masri says he has been traumatised by his experiences
Khaled al-Masri had been appealing against the decision of lower courts not to hear his case against the CIA on national security grounds.
Mr Masri says he was abducted in Macedonia in 2003 and flown to Afghanistan for interrogation.
His case has highlighted the CIA's "extraordinary rendition" programme.
The Supreme Court's decision "terminated" Mr Masri's lawsuit and was issued without comment, The Associated Press news agency notes.
Correspondents say the decision will be seen as an endorsement of the Bush administration's argument that state secrets would be revealed if the case were allowed to proceed.
In his lawsuit, Mr Masri was seeking damages of $75,000 (£37,000).
The 44-year-old alleges he was tortured during five months in detention, four months of which were spent in a prison in Kabul, Afghanistan, nicknamed the "salt pit".
On his flight to Afghanistan, he says, he was stripped, beaten, shackled, made to wear "diapers", drugged and chained to the floor of the plane.
By his account, he was finally released in Albania after the Americans realised they had got the wrong man.
He told the BBC in February he had been "traumatised" by his experiences.
Last month, Germany reportedly dropped a request to the US to extradite 13 suspected CIA agents accused of abducting him.