Army Col. Denise Lind, who is overseeing Manning's pretrial hearings at Fort Meade, Md., also said in her ruling Wednesday that Manning's defense can present evidence that the former intelligence analyst chose to leak documents that wouldn't harm national security, The Washington Post reported.
A court-martial is scheduled for June for the 25-year-old Manning, charged with leaking sensitive government cables and other documents to the whistle-blowing website WikiLeaks, which published them on its website and shared them with media outlets.
Because of Lind's ruling, damage assessments by intelligence agencies after WikiLeaks released the hundreds of thousands of documents will not be admitted into evidence by either side during the court-martial.
Among the charges filed against Manning is aiding the enemy.
Prosecutors had indicated they plan to offer evidence recovered from al-Qaida founder Osama bin Laden's compound that proves he asked for and got access to some of the WikiLeaks material Manning allegedly leaked.
Manning was arrested in May 2010 in Iraq and eventually transferred to the military jail at Quantico, Va. During his confinement, Manning was held in solitary confinement and denied clothing on occasion. Lind recently ruled that any sentence he receives should be reduced by 112 days because of the conditions of his confinement.
Manning's lawyer, David Coombs, said Wednesday witness testimony is likely to be less reliable because of the time that has passed since the alleged offenses.
"It is just common sense to say, witnesses will say, 'It has been several years, I don't recall,'" Coombs said.