A California appeals court sided with one of the largest fruit farms in the nation, ruling that a law allowing the state to order unions and farming companies to reach binding contracts was unconstitutional.

Labor activists say the mandatory mediation and conciliation law is a key to helping farm workers improve working conditions.

However, the 5th District Court of Appeal said Thursday it does not clearly state the standards that the contracts are supposed to achieve.

The ruling came in a fight between Gerawan Farming and the United Farm Workers, the union launched by Cesar Chavez. The union won the right to represent Gerawan workers in 1992, but the two sides did not agree to a contract.

At the union’s request, the state Agricultural Labor Relations Board in 2013 ordered Gerawan and the UFW to enter into binding mediation. The two sides couldn’t come to an agreement so a deal was crafted by the mediator and adopted by the labor relations board, the appeals court said. Gerawan objected to the terms.