WASHINGTON - A federal judge in the CIA leak case set limits on the ability of Vice President Dick Cheney's former chief of staff to challenge prosecutors who are reluctant to provide classified information to the defendant.

Lawyers for I. Lewis "Scooter" Libby are seeking a substantial amount of highly classified material from the government so the former White House aide can defend himself against five counts of perjury, obstruction and lying to the FBI.

The government wants to delete some classified information from documents Libby is seeking and wants to provide summaries for language in other highly sensitive classified documents.

U.S. District Judge Reggie Walton said Wednesday the government may in some instances present the court the actual classified information that Libby wants for his defense without letting the defendant and his lawyers see it, or the government's arguments for withholding it.

The judge would then determine whether some of the deletions or substitutions that the government is making are proper.

"Despite the fact that the defendant is a former national security official and some of his defense team hold security clearances, this does not entitle them to view documents that exceed the level of their security clearances or documents that may discuss particularly sensitive issues with profound national security implications," the judge wrote.

However, Walton set limits on the government's efforts to deal exclusively with the judge to determine whether classified information Libby is seeking is material to his defense.

"It is inappropriate and in fact unnecessary for the government to argue questions of materiality" without letting Libby's legal team know what the arguments are, Walton wrote.

Libby is accused of making false statements about how he learned of the CIA employment of covert officer Valerie Plame and what he told reporters about her connection to the agency. Plame's identity was publicly disclosed in 2003, eight days after her husband accused the Bush administration of twisting prewar intelligence to exaggerate the Iraqi threat from weapons of mass destruction.

Commentary: