Good question

from Brian Beutler:
"The relevant question to my mind is whether the administration is hampering the process [of releasing Guantanamo detainees] so that some of these guys don't someday describe the torture techniques used against them to a lawyer or a judge or the media. If that's the case, then you can be sure the administration will do anything in its power to keep these guys in military custody for as long as possible."

Actually, the government has already made this very argument in court:

"The Justice Department argued this point explicitly last November, in the case of a Baltimore-area resident named Majid Khan, who was held for more than three years by the C.I.A. Khan, the government said, had to be prohibited from access to a lawyer specifically because he might describe the “alternative interrogation methods” that the agency had used when questioning him. These methods amounted to a state secret, the government argued, and disclosure of them could “reasonably be expected to cause extremely grave damage.” (The case has not yet been decided.)"