A judge on Tuesday overturned a Los Angeles ordinance requiring grocery store operators to retain workers for 90 days after a store changes ownership.

The ruling was a major victory for grocery store owners in a hard-fought battle with city officials and labor interests.

Los Angeles County Superior Court Judge Ralph Dau ruled that the 2005 ordinance was unconstitutional. He found that it conflicts with existing state laws and is therefore pre-empted by the state retail food code. Dau also ruled that it discriminates between grocery stores on the basis of size and whether they have collective bargaining agreements.

The ordinance was hastily crafted in response to reports at the time that Albertson’s Inc. chain, with more than 300 stores in Southern California, was close to accepting a buyout offer. It was passed after a strong push by local unions and living wage advocates and marked the first attempt by the city to regulate workforce issues at companies not doing business directly with the city.

The ordinance applied to supermarkets at least 15,000 square feet in size and can be superseded by a collective bargaining agreement. Judge Dau ruled that these two provisions violated the equal protection guarantees of both the U.S. and California constitutions.

L.A. Mayor Antonio Villaraigosa signed the ordinance into law in January 2006 and the California Grocers Association filed suit to block its implementation.

Jill Rulon, California Grocers Association acting president, said the organization was “satisfied” with the ruling.

“Since the Grocery Worker Retention Ordinance has been in effect, sales of grocery stores from one operator to another in the City of Los Angeles have ceased,” she said. “Stopping the growth of new retail was just one of the many harmful impacts this law had on city residents.”

Backers of the ordinance weren’t pleased.

“We’re disappointed in the ruling, and are reviewing our options,” said Nick Velasquez, spokesman for the Los Angeles City Attorney’s Office.

Roxana Tynan, deputy director with Los Angeles Alliance for a New Economy, one of the chief sponsors of the ordinance, hinted at an appeal.

“We continue to feel that we are on solid ground legally and that we will ultimately prevail on this ordinance,” Tynan said. “Worker retention ordinances have been upheld in many cities throughout the state.”