Presumably there's a good reason: national security.
Having survived his exposure to second-hand smoke, Nashiri was exposed to the most serious unauthorized interrogation technique documented by the IG.
"Sometime between 28 December 2002 and 1 January 2003, the debriefer used an unloaded semi-automatic handgun as a prop to frighten al-Nashiri into disclosing information," said the IG report. "After discussing this plan with (redacted) the debriefer entered the cell where al-Nashiri sat shackled and racked the handgun once or twice close to al-Nashiri's head.
"On what was probably the same day," the report continued, "the debriefer used a power drill to frighten al-Nashiri. With (redacted) consent, the debriefer entered the detainee's cell and revved the drill while the detainee stood naked and hooded. The debriefer did not touch al-Nashiri with the power drill."
Now, this truly idiotic behavior led the CIA's inspector general to conscientiously refer the case to the Criminal Division of the Justice Department -- six years ago, immediately after it happened. The Justice Department declined to prosecute.
Other reported instances in which CIA interrogators used unauthorized techniques did not merit a separate IG investigation, according to the report. "These included the making of threats, blowing cigar smoke, employing certain stress positions, the use of a stiff brush on a detainee and stepping on a detainee's ankle shackles," said the report. "For all of the instances, the allegations were disputed or too ambiguous to reach any authoritative determination regarding the facts."
In the end, the IG dodged a definitive judgment on the productive value of the enhanced interrogation techniques that the Justice Department did approve for use by the CIA, saying that the "effectiveness of particular interrogation techniques in eliciting information that might not otherwise have been obtained cannot be so easily measured."
But CIA interrogations of detainees, according to the report, did uncover plots against the U.S., including plans to "loosen spikes in an attempt to derail a train," "blow up several gas stations to create panic and havoc," "hijack and fly an airplane into the tallest building in California in a west coast (sic) version of the World Trade Center attack" and "cut the lines of suspension bridges in New York in an effort to make them collapse."
In the eight years since Sept. 11, 2001, al-Qaida has not managed to strike America again. As a reward for the CIA's part in this success, President Obama has now stripped the agency of its lead role in questioning terrorists and Attorney General Eric Holder has named a special prosecutor to investigate its interrogation practices.