Monday's ruling arose from a pair of prison class-action lawsuits, one going back 20 years, which accused the state of failing to provide decent care for prisoners who were mentally ill or in need of medical care. The two suits were combined by a panel of three judges, all of whom were veterans with a liberal reputation.
U.S. District Judges Thelton Henderson from San Francisco and Lawrence Karlton from Sacramento were joined by 9th Circuit Judge Stephen Reinhardt from Los Angeles. Since overcrowding was the "primary cause" of the substandard care meted out to inmates, they ordered the state to reduce its prison population by 38,000 to 46,000 persons.
Then-Gov. Arnold Schwarzenegger and then-Atty. Gen. Brown appealed, believing a more conservative Supreme Court would be wary of telling a state how to run its prisons.
Since the earlier court order, the state has transferred about 9,000 state inmates to county jails. According to recent figures, the total prison population is about 33,000 more than the limit of 110,000 set by the three-judge panel. Kennedy said state officials can decide how to reduce the number of inmates.
The American Civil Liberties Union said the court "has done the right thing" by addressing the "egregious and extreme overcrowding in California's prisons."
Donald Specter, the lawyer for the nonprofit Prison Law Office who represented the inmates, said "this landmark decision will not only help prevent prisoners from dying of malpractice and neglect, but it will make the prisons safer for the staff, improve public safety and save the taxpayers billions of dollars."
Others agreed with the dissenters. "What is the message for law-abiding people in California? Buy a gun. Get a dog. Put in an alarm system. Even seriously consider bars on the windows," said Kent Scheidegger of the Criminal Justice Legal Foundation in Sacramento, writing on his "Crime & Consequences" blog.
Meanwhile, the court took no action Monday on another California case, a challenge to the state's policy of granting in-state tuition at its colleges and universities to students who are illegal immigrants and have graduated from its high schools.
The justices said they would consider the appeal in a later private conference.
Times staff writer Anthony York contributed to this report.