Hassan Mustafa Osama Nasr, an Egyptian imam known as Abu Omar, was snatched from a Milan street in 2003 and flown to Egypt for interrogation, where he says he was tortured for seven months. He was resident in Italy at the time of the kidnapping.
Rendition was first authorized by former US President Bill Clinton in the 1990s, and it was stepped up after ex-US President George W. Bush declared his so-called “war on terror” following the September 11, 2001 attacks.
Italy's highest appeals court has upheld the guilty verdicts on 23 Americans for the kidnapping of an Egyptian Muslim cleric in Milan.
In Wednesday’s ruling, the defendants were all tried in absentia in one of the world’s biggest court cases against the US “extraordinary rendition” program.
The Americans - 22 of whom were CIA agents and one an Air Force pilot - are believed to be living in the United States and are unlikely to serve their sentences.
The group includes the former station chief of CIA operations in Milan, Robert Seldon Lady.
All of the Americans were originally sentenced to seven years' jail by a lower court, apart from Seldon Lady, who was given a nine-year sentence.
Italy's top court also said on Wednesday that two former heads of Italy's SISMI military intelligence agency, Nicolo Pollari and Marco Mancini, should be re-tried.
The two had been acquitted by the appeals court in 2010 in a ruling that said producing evidence against them would have violated state secrecy laws.
Three lower-level Italian agents will also be re-tried, the court said.
The court also upheld a two-year-and-eight-month prison sentence against former military intelligence officials Pio Pompa and Luciano Seno.