SACRAMENTO -- Three months after Gov. Arnold Schwarzenegger signed a bill allowing local governments to regulate the neutering, spaying and breeding of specific dog breeds, the measure has finally become state law after a referendum drive to overturn it fell short.

Senate Bill 861, authored by state Sen. Jackie Speier, D-San Mateo/San Francisco, would have become effective on Jan. 1, but a referendum drive to overturn the law left it in limbo.

However, the referendum petition failed to garner the 373,000 signatures needed to overturn SB 861, and the bill went into effect late Thursday, Speier's staff director Richard Steffen said.

The "bill allows cities and counties to pass specified breed-specific legislation for mandatory spaying and neutering, and breeding restrictions," according to California state Senate floor analysis.

Speier and San Francisco Mayor Gavin Newsom pushed for the bill's passage following the fatal mauling of 12-year-old Nicholas Faibish by his family's pit bull in June 2005.

In November, the San Francisco Board of Supervisors unanimously approved an ordinance that requires the neutering or spaying of pit bulls in San Francisco.

"The city and county of San Francisco has already adopted an ordinance that should serve as a statewide model for municipalities with public safety problems associated with a growing population of unwanted pit bulls," Speier said in a statement.

Steffen said that, while many look at SB 861 as an attack on pit bulls, the bill itself is not pinpointing any breeds in particular. Rather, it gives a city or county the right to do so.

The bill "didn't declare that pit bulls are dangerous or call for a ban on pit bulls," Steffen said. "It's just a spay-and-neuter bill."

Scott Delucchi, spokesman for the Peninsula Humane Society and Society for the Prevention of Cruelty to Animals, said pit bulls are a common target in the Bay Area and that nearly 70 percent of dogs in Bay Area shelters are pit bulls and pit bull mixes.

In contrast, Delucchi said that when the Disney film "101 Dalmatians" came out in the 1990s, the PHS/SPCA was overrun with Dalmatians. Had SB 861 been around at that time, then it's possible Dalmatians would have been the breed in question and not pit bulls, he said.

Delucchi did note that while the neutering or spaying of a dog can't guarantee it won't attack a person, studies have shown that "somewhere around 90 percent of animals that attack are intact males."

The less testosterone any animal has, be it a pit bull, poodle or golden retriever, the less aggressive it's likely to be, according to Delucchi.

"We're not saying that (spaying and neutering is) going to protect people 100 percent from being attacked by a dog," but the chances are reduced, Steffen said.

Delucchi said that all SB 861 suggests is that certain breeds will be permitted into a given area only if they are spayed or neutered.

The bill could have been open-ended and "given a city the opportunity to say 'you can own a pit bull in our city but you have to take a $1 million insurance policy out or you can't live within five miles of a school if you own a certain type of dog,' but this bill doesn't do that," Delucchi said.

The bill merely looks to reduce an unwanted population of dogs, and right now in the Bay Area that breed just happens to be pit bulls, he said.

According to Delucchi, now that SB 861 has become law, it will be interesting to see how San Francisco enforces its ordinance.

"It's not like all the pit bull owners are going to get in line to get their pit bulls altered," Delucchi said.

However, if pit bull owners do decide to do so, the PHS/SPCA is offering free pit bull alteration surgeries to San Mateo County residents, Delucchi said.