The Pacific Legal Foundation on Wednesday said that it has petitioned the U.S. Supreme Court to review and reject the City of Los Angeles’ grocery worker retention ordinance.

The group argues in its petition to the High Court that ordinance approved in 2005 illegally denies new grocery store owners the right to hire their own employees unless they also agree to maintain a unionized workforce.

The ordinance applies to companies that purchase grocery stores of 15,000-square feet or larger to hire employees only from existing staff, and retain them for at least 90 days. The restriction doesn’t apply if the new owner consents to a collective bargaining agreement with a union.

The conservative foundation’s attorneys filed the petition on behalf of the California Grocers Association, a trade organization representing more than 450 companies operating more than 6,000 stores statewide.

“This law is a brazen scheme to punish non-union employers,” said PLF Principal Attorney Timothy Sandefur in a statement. “The National Labor Relations Act bars states and local governments from interfering with the bargaining of unions and employers, yet that’s exactly what L.A. has done through this ordinance.”

The California Supreme Court in July upheld the 2005 ordinance, overturning lower court decisions that had sided with grocery store owners.

Union officials have not yet issued a response to the petition.