Gov. Arnold Schwarzenegger made a mistake, and he is trying to correct it. Now the Legislature is stepping in to help him finish the job. If they succeed together, their work will stand as a model for finding humane ways to reduce the recent rapid growth in state spending.

The governor's error came in December, when he proposed repealing a law that makes services to the developmentally disabled an entitlement. The Lanterman Act, as the law is known, is the heart of California's unique commitment to people born with brain disabilities that prevent them from participating as normal members of society.

The law guarantees state services to those with mental retardation, autism, cerebral palsy and other ailments, always with the goal of keeping them in the least restrictive setting possible. The services are provided by 21 semi-independent regional centers without regard to the ability of the client or his or her family to pay.

Schwarzenegger's mistake was in not realizing that trying to limit the number of people who can get these services was a losing proposition politically that would only distract attention from his true goal: trying to restrain the recent rapid growth in the cost of the program. As Senate President Pro Tem John Burton said, people don't get over developmental disabilities. There's no cure for this condition. So setting caps means that new clients - mainly children - who need services have to wait for somebody else to die. That's a tough position to defend.

A few weeks after he made the proposal, Schwarzenegger withdrew it. But that didn't alter his determination to rein in the costs. And looking at them, it's not hard to see why.

The number of people served by the Department of Developmental Services, and the cost per person, are both climbing fast. According to the non-partisan Legislative Analyst, caseload growth in community services for the developmental disabled - that's everyone in the program who is not confined to an institution - has risen at three times the rate of California's population growth in the past five years.

On top of that, the cost-per-client in these programs is also rising - at an unsustainable rate. The cost has risen from about $9,500 per person in 1998 to $13,400 today. That's a 41 percent increase.

Combined, the increased number of people being served and the higher cost-per-client have driven the size of the program's budget to more than $3 billion, about $2 billion of which comes from the state's debt-ridden general fund.

Schwarzenegger has now proposed a number of cost-saving measures that would slow the growth in spending while still serving the same number of clients.

Currently, the regional centers operate with relatively little oversight from the state. The governor wants the state to set standards, and in some cases rates, for the purchase of services by the centers - for such things as transportation and day care. He also is calling for co-pays for families who have the ability to share in some of the cost of the services provided to their children.

At a special hearing last week of the Assembly Budget Committee, lawmakers from both parties joined Schwarzenegger administration officials in an intensive review of the program and the potential savings.

Much of the focus was on the possibility of finding more federal funds to support the program. Various estimates suggest that more than $100 million a year might be available if California changes some of its rules and more aggressively seeks the money.

That would be a helpful stopgap measure. But without reforms, the cost of the program will still be growing faster than the state taxpayers' ability to pay for it.

The lack of statewide standards means that services and costs vary widely - as much as 30 percent - from one area to the next. And even when a regional center denies a service to a client, the client can appeal that decision to administrative law judges who have wide discretion to overrule the center's administrators.

According to the Legislative Analyst, these judges sometimes order the centers to pay for things that would normally be the responsibility of a family whether or not they had a disabled child. In one case, for example, a regional center was required to pay for private swimming lessons even though the center had determined that group lessons would be better for the client. In another case, a judge ordered the center to pay a portion of the cost for the addition of a bedroom and bath to a private home.

And without statewide rates, the cost of the most serious cases is difficult for the regional centers to control. In 21 cases statewide, officials said, taxpayers are paying more than $200,000 a year to provide intensive services in a home-based setting, sometimes with as many as three full-time aides to assist a single person.

A bipartisan consensus to seek more federal money for these services while exercising more oversight on how the program operates would allow the state to keep its commitment to the developmentally disabled without breaking the bank. It would be good for the disabled, and for the taxpayers.