A California judge on Thursday ruled that Gov. Arnold Schwarzenegger had abused his discretion in ordering furloughs of state workers, dealing a blow to the administration's efforts to cope with the state's ongoing fiscal crisis.

Alameda County Superior Court Judge Frank Roesch said the administration must halt the furloughs for workers represented by three unions, including Service Employees International Union Local 1000, which represents 95,000 state employees.

SEIU spokesman Jim Zamora said the ruling could affect up to 50,000 employees across state government who work at so-called "special fund" agencies, or those that receive money from sources other than the state general fund.

It was not immediately clear whether the decision would apply to employees not represented by the three unions that brought the case.

Roesch ruled against Schwarzenegger's furlough orders on two fronts: He said the administration could not take the action against employees in special fund agencies. He also said Schwarzenegger had overstepped his authority by claiming the furloughs were necessary to deal with a budgetary emergency.

Roesch said the governor can overstep the Legislature's normal authority in an emergency only for a temporary period, a period the judge said ended once the Legislature approved the state budget.

"The Executive Orders themselves appear to recognize that the emergency necessitating them was the failure of the Legislature to pass the budgets, though the reach of the orders extended long after those budgets were subsequently passed and signed into law," the judge wrote.

Schwarzenegger this year forced most state employees to take three days off a month without pay as the state faced a massive budget deficit. The mandatory furloughs, which began in February and were extended over the summer, affected about 200,000 state workers and were expected to save the state $2 billion.

Schwarzenegger spokesman Aaron McLear said the administration would appeal Thursday's decision.

"In these tough economic times, there's no reason why state workers should be shielded from the same economic reality that the rest of the state faces," he said.

An appeal would automatically stay the ruling, although union leaders said they intend to ask the judge to immediately implement the order because state employees are suffering financially.

Union attorney Felix De La Torre said he and other union representatives were analyzing the ruling to determine whether it also would apply to workers in general fund agencies.

He estimated the state could owe workers at least $100 million in back pay if the ruling is upheld on appeal.