Gov. Jerry Brown says he will ask the courts to stay what he calls an "unprecedented order" to release nearly 10,000 prison inmates by year's end.
A panel of federal judges on Thursday rejected Brown's attempt to circumvent its long-standing order to reduce California's prison population.
It's the latest step in an ongoing legal drama over how to improve inmates' medical and mental health care.
The judges ordered Brown to expand good-time credits leading to early release as part of a plan to reduce prison crowding.
The governor has already filed notice that he intends to appeal Thursday's order to the U.S. Supreme Court.
The federal judges stopped short of citing the Democratic governor for contempt, but they again threatened to do so if he does not immediately comply with their latest order.