Critics of California Insurance Commissioner John Garamendi's proposed changes to regulations governing how auto insurance rates are determined say the courts have already ruled against the changes.

At the center of the criticism is Mr. Garamendi's proposal to seek a rule change that would put more emphasis on a driver's record in determining premium rates rather than his or her location and other factors.

Current California law says that the three required factors for determining auto insurance rates (driving record, annual miles driven and years of driving experience) cannot be outweighed by the average weight of a list of a number of other factors that include the ZIP code where the car is located, marital status or additional insurance coverage a driver may have with one carrier.

Steve Young, general counsel for the Insurance Brokers and Agents of the West, said legal battles over this issue date back to 1990, when then insurance commissioner Roxani Gillespie sought to implement the language of Proposition 103 (an auto insurance reform initiative passed by voters in 1988) literally. The language of the proposition, Mr. Young noted, was "ambiguous at best" in terms of assigning importance to auto factors. It said only that the factors for determining auto insurance rates should be considered, "in descending order of priorities," with the mandatory factors listed afterward.

Commissioner Gillespie's plan was challenged by the insurance industry. The State Superior Court in Los Angeles sided with the industry.

Commissioner Garamendi's proposal would change the system by barring any optional factor from being given more weight than any mandatory factor. Sam Sorich, president of the Association of California Insurance Companies, an affiliate of the Property Casualty Insurers Association of America (PCI), said Mr. Garamendi's proposal is similar to a proposal on the issue he released two years ago.

At that time, Mr. Sorich said, the PCI asked an independent actuary to examine how the proposal would affect auto rates for consumers across the state. He said the actuary found that rates for 62 percent of California drivers would increase "largely because of the diminished weight given to where a car is garaged."

"We know based on actuarial analysis that appropriate weight given to where a car is garaged is greater than any single mandatory factor," Mr. Sorich added. "If companies have to ignore this reality, we think that the result will be unfairness to drivers."

Challenges from the industry have been based on the non-discriminatory issue, which Mr. Young said was based on "fundamental fairness" that those living in more densely populated areas should not have their insurance subsidized by those living elsewhere.

"If what happened in the past happens again," Mr. Young said of efforts to assign increased weight to the mandatory rating factors, "then I don't see why the result would be any different."

The timing of commissioner's Garamendi's proposal raised other concerns.

Mr. Sorich noted that California currently has a "vital, vibrant and competitive market," that could potentially be disrupted by rate increases if the proposal were enacted.

"Any time you change the rules of the game, it creates marketplace dislocation and confusion," as large numbers of consumers suddenly find themselves facing significant increases to their premiums, pointed out Mr. Young.

"Guess who gets to explain it to them," he said. "It's not the insurance commissioner, or even the insurance companies, really. It's the agent or broker."