SACRAMENTO  (AP) — A federal judicial panel's threat to place Gov. Jerry Brown in contempt of court if he fails to comply with a mandated prison population reduction is a rare move, legal observers said Friday.

The ruling came more than three years after the state was ordered to reduce its inmate population to improve medical and mental health care.

The three-judge panel acknowledged on Thursday that the state has taken significant steps to reduce its inmate population but said it still expects the state to be 9,000 prisoners over the court-mandated cap by the end-of-year deadline.

Despite the threat, the federal court may have little power to enforce its judgment against state officials because it's not unheard of for a governor to defy court rulings, Mary-Beth Moylan, a professor at the University of the Pacific's McGeorge School of Law in Sacramento, said in an email Friday.

Contempt orders are rarely used as an enforcement mechanism because "it's more of a symbolic punishment," she said.

Naming Brown, the ruling said state officials must take whatever steps are necessary to comply or face the consequences.

Otherwise, "they will without further delay be subject to findings of contempt, individually and collectively," it said.

Don Specter, who is suing the state over prison crowding, said the judges have shown extraordinary patience with Brown but signaled in the ruling that they are willing to force him to comply.

"They made clear in yesterday's order that they've just had it," Specter said in an interview Friday. "It's clear from the court's opinion they view the governor as the main person who's involved in setting the strategy for the state."

In response to Thursday's ruling, the Democratic governor told California reporters traveling with him in China that he will appeal the decision.

"We have, I believe from what I'm being advised, among the best health care in America and probably in the world." Brown told The Sacramento Bee. "Now the judge sees it differently, and all I can say is I respect his differences, but we will take our case to the higher courts."

Specter said the federal panel could fine the governor or issue an order taking control of prisons from him.