Its a gray area because the Italian government authorized it. The CIA agents were not acting alone. Just like if the government decided to use the FBI to take someone into custody in America. The CIA in Italy assisted the Italian government.
I don't think its grey at all, frankly. Given that the Italian government was assisting, and this was an intelligence operation the CIA agents are absolutely not guilty. That being said, the Italians government has never said they were behind Imam Rapito and at least on paper denies any involvement.
IMHO what the courts are really aiming for is for the US to say the Italian government authorized it. This case is IMHO a perfect example of what executive pardons are for, the civilian judiciary is budding into national security.
As far as the extradition aspect while I can understand in theory conducting a trial in absentia, I can't understand any logic behind conducting an appeal.
So since we've expanded:
a) I think the trial (of the CIA agents) was political and didn't really get to the main issue, a questionable trial.
b) I think the appeal is an abuse of process.
c) I think (a) and (b) shows the serious problems with Italian justice
d) I think the Rapito affair did influence jurors on the Knox trial.
e) I think despite a,b,c the USA is in violation of our extradition treaty by refusing to extradite.
f) I think the people who ordered Rapito did violate the statues against kidnapping and torture, though they are likely high placed political persons. I suspect VP Cheney.
Whew. Anyway except for point (d) this is getting afield. Is it allowed?