In an April 24, 2009, ruling, the Alameda County Superior Court ruled that chemicals identified in worker safety standards as carcinogens and reproductive toxicants must be listed under Proposition 65 without further review. The California Chamber of Commerce argued that the provision was a time-limited option applicable only when the initial Proposition 65 list of chemicals was adopted in 1987. According to the court, Proposition 65 "imposes a clear ministerial duty" to list chemicals linked to cancer and reproductive harm already identified in labor codes "without further review" and to update the Proposition 65 list annually. A spokesperson for the California Chamber of Commerce said it will appeal the ruling. The court has yet to rule on the related issue of whether the Office of Environmental Health Hazard Assessment (OEHHA) can list chemicals based solely on threshold limit values (TLV) adopted by the American Conference of Governmental Industrial Hygienists (ACGIH). The California Chamber of Commerce contends that if other authoritative bodies cited in Proposition 65 have not identified an ACGIH chemical as a carcinogen or reproductive toxicant, that chemical cannot be added to the list via the labor code mechanism without undergoing a scientific review by the state's expert panel. Oral arguments on the ACGIH issue will be held on May 27, 2009.

A coalition of environmental and labor groups, including the Sierra Club, Natural Resources Defense Council, and United Steelworkers filed suit on November 19, 2007, accusing California of failing to enforce Proposition 65 by refusing to allow the Cancer Identification Committee to review independently chemicals for listing and not using other mechanisms to list chemicals. In a separate suit, the California Chamber of Commerce challenged OEHHA's application of the labor code mechanism to add chemicals to Proposition 65. The suits were consolidated in Sierra Club v. Schwarzenegger. In addition to the ACGIH issue, the court has yet to rule on the environmental and labor groups' claims that OEHHA has "unreasonably delayed consideration of chemicals" for listing. Environmental and labor plaintiffs want more than 90 chemicals already identified in workplace safety standards added to the Proposition 65 list, including styrene, gasoline additives such as tert-amyl methyl ether, and carbaryl.

To clarify the listing process via the labor code mechanism, OEHHA has proposed to adopt a regulation that would clarify the procedures used to determine which chemicals qualify for the labor code listing process. OEHHA has not yet issued a final regulation.