In pretrial motions, the state sought to prohibit public disclosure of certain documents classified as sensitive communications or part of internal deliberations.
Inmate advocacy groups that brought the lawsuits opposed the administration's request, and federal Magistrate Judge John Moulds in Sacramento issued a ruling Friday generally siding with the plaintiffs and limiting the administration's request.
The Associated Press also filed written opposition with the court, saying the administration's motion was too broad and had the potential to improperly keep some records from the public eye.
For example, the administration sought to define sensitive communications as those that include "budget change proposals for government agencies that are not defendants in this proceeding."
Moulds said only documents that clearly would jeopardize prison security if they were made public should remain secret. He also ruled that any personal information on inmates and state employees would be redacted.
The administration can appeal Moulds' decision to the three-judge panel.
"We disagree with the ruling and are currently reviewing our options for how we will proceed," Rachel Cameron, a spokeswoman for Gov. Arnold Schwarzenegger, said Friday.
California's 33 adult prisons were designed for roughly 100,000 inmates but currently hold 159,000. Inmate advocacy groups say the crowding has led to numerous problems, including neglectful health care and poor mental health treatment.
The ruling comes as court-appointed referees attempt to negotiate a settlement that would avoid a trial. Under the proposed settlement, 27,000 inmates would be released before serving their full sentences and a population cap would be set in place.
Republican state lawmaker who have intervened in the lawsuit will reject any settlement that includes a prison cap formula, said state Sen. George Runner. He said Republicans agree that crowding needs to be reduced but believe it can be done by adding nearly 38,000 new prison and county jail cells through a building program approved by the Legislature last year.
In addition, a federal receiver is seeking $7 billion in state money to add 10,000 hospital and mental health beds.