A Sacramento Superior Court judge issued a tentative ruling Thursday that the Schwarzenegger administration exceeded its authority in suspending parts of the state’s new nurse staffing law handing a victory to one of the governor’s fiercest critics.

Judge Judy Holzer Hersher sided with the California Nurses Association in finding that that last year’s emergency order relaxing certain provisions of the law were not warranted because they were not supported by adequate evidence, including claims the law was leading to hospital closures.

“In sum, the determination of ’emergency’ is arbitrary and capricious and entirely lacking in evidentiary support,” the judge said in her ruling. State attorneys will have a chance to challenge the ruling at a Friday hearing, but tentative rulings are not often reversed.

Health and Human Services Agency Secretary S. Kimberly Belshe issued a statement on behalf of the governor, saying the emergency order was “based on a solid legal foundation.” If the judge does not reverse herself in the final ruling, “the Department of Health Services intends to pursue all legal remedies,” she said.

The regulations went into effect last year and call for a minimum number of nurses on the floor for each patient, depending on the ward. Among the provisions suspended by the governor was a requirement that hospitals maintain nurse-to-patient ratios “at all times,” even when nurses went on short breaks.

In a written statement, California Nurses Association Executive Director Rose Ann DeMoro called the ruling “monumental news for all California patients and hospitals who need hospital care and it tells Gov. Schwarzenegger that he has no authority to overturn legislation to protect the public simply to please his donors.”