After he is no longer a Govt. Official can he be sued?
Further Evidence Rumsfeld Implicated in War Crimes
Please read this important post by Marty Lederman, Army Confirms: Rumsfeld Authorized Criminal Conduct.
Here's a key section, but there's more:
The Army's charges against Jordan reflect the view, undoubtedly correct, that the use of forced nudity or intimidation with dogs against detainees subject to military control constitutes cruelty and maltreatment that Article 93 makes criminal. It doesn't matter whether they are or are not "torture," as such; nor does it matter whether the armed forces should be permitted to use such interrogation techniques: As things currently stand, they are unlawful, as even the Army now acknowledges.
But then how can we account for the actions of the Secretary of Defense and his close aides?
On November 27, 2002, Pentagon General Counsel William Haynes, following discussions with Deputy Secretary Wolfowitz, General Myers, and Doug Feith, informed the Secretary of Defense that forced nudity and the use of the fear of dogs to induce stress were lawful techniques, and he recommended that they be approved for use at Guantanamo.
(The lists of techniques to which Haynes was referring can be found in this memorandum.) On December 2, 2002, Secretary Rumsfeld approved those techniques for use at Guantanamo -- and subsequently those techniques were used on detainee Mohammed al-Qahtani.
In other words, the Secretary of Defense authorized criminal conduct.
...
Today's Army charge under UCMJ Article 93 against Lt. Col. Jordan -- for conduct that the SecDef actually authorized as to some detainees -- demonstrates that Rumsfeld approved of, and encouraged, violations of the criminal law.
http://www.discourse.net/archives/2006/04/further_evidence_rumsfeld_implicated_in_war_crimes.html