Skip to content

Federal Judge Prohibits Enforcement of Proposition 65 Warning Requirement for Glyphosate – But The Devil Is in The Details

An ongoing lawsuit against California’s Office of Environmental Health Hazard Assessment (OEHHA) and the California Attorney General reached a critical point on February 26, 2018, when a federal district court applied First Amendment principles to prohibit the enforcement of the Proposition 65 warning requirement for glyphosate. (National Association of Wheat Growers, et al. v. OEHHA, et al. (Eastern District California Case No. 2:17-2401 WSB EFB).) The ruling is notable for its acknowledgement that the glyphosate listing does not reflect worldwide scientific consensus regarding the chemical’s actual cancer risk. However, the prohibition on enforcement may not be as broad as the regulated community thinks or hopes.

Under Proposition 65, formally the Safe Drinking Water and Toxic Enforcement Act of 1986, “clear and reasonable” warnings are required for exposures to chemicals identified on the Proposition 65 list of carcinogens and reproductive toxicants. Glyphosate, a widely used herbicide produced by Monsanto Company, was listed as a Proposition 65 carcinogen in July 2017 based on a designation by the International Agency for Research on Cancer (IARC) that the substance is a probable human carcinogen. This designation was controversial, in that IARC’s designation procedure was fraught with inconsistencies that were revealed only after IARC published its conclusion. Indeed, numerous agencies around the world have evaluated the substance and have concluded that glyphosate does not cause cancer. OEHHA itself evaluated glyphosate years ago and concluded that the substance does not present a cancer risk. Thus, OEHHA’s listing represents the sole designation in the world, after years of evaluations and contrary conclusions, that glyphosate may be a human carcinogen.

Monsanto and a number of trade associations filed a federal lawsuit in the Eastern District of California against OEHHA and the California Attorney General, arguing (among other things), the Proposition 65 warning requirement for glyphosate violates the plaintiffs’ First Amendment rights because the warning would require them and their members to state unequivocally that glyphosate is a known carcinogen even though there is no scientific consensus on the matter. U.S. District Court Judge Shubb issued a preliminary injunction prohibiting the State (and those in privity with the State, like private enforcers) from enforcing the glyphosate warning on the grounds that “it is inherently misleading for a warning to state that a chemical is known to the state of California to cause cancer based on the finding of one organization…when apparently all other regulatory and governmental bodies have found the opposite.”

The ruling is not a final decision, and although the warning mandate for glyphosate is suspended while the case proceeds, it will continue to be listed as a Proposition 65 carcinogen until further notice. This aspect of the court’s order is notable, since it means that the little-enforced Proposition 65 discharge prohibition, which prohibits the discharge of listed chemicals into drinking water or onto land where the chemical may pass into a source of drinking water, still may be enforced. As an agricultural chemical that may be contained in agricultural run-off, glyphosate’s continued listing therefore still presents a Proposition 65 enforcement risk.

Moreover, the wording of the court’s order suggests that the prohibition on enforcing the warning requirement may not be as broad as the regulated community would like. The prohibition benefits “plaintiffs, plaintiffs’ members, and all persons represented by plaintiffs.” It would appear that the warning requirement still could be enforced against those entities who are not covered by those categories.

Proposition 65 has frequently been criticized not only for being overly burdensome to businesses, but also for failing to be of use to consumers because warnings fail to provide context and meaningful information. Critics of the law have argued that labeling products with low health risks as dangerous reduces the impact of warnings on products that pose genuine health risks. The glyphosate listing appears to be the poster child for this pervasive problem.


This blog article was researched and written, with Ann Grimaldi, by Brown University Class of 2018 student Aisha Keown-Lang. Ms. Keown-Lang is studying biology and political science at Brown University with the goal of going into bioethics and public health. Her special interest in genetics stems from her research in the Li Lab at UCSF and the Gerbi Lab at Brown. After having worked with children in the Providence school system for nearly three years, her commitment to improving scientific literacy and expanding health services in underserved communities remains strong. Ms. Keown-Lang is currently a writer for Brown’s Science Cartoon Program (SciToons), which aims to communicate scientific research and ideas to a diverse audience.

This is attorney advertising. Please see disclaimer.

Ms. Grimaldi maintains a diverse environmental law practice focusing on chemical and product regulation and litigation defense. Her practice areas include Proposition 65, California's Safer Consumer Products Regulations, California's Rigid Plastic Packaging Container Act and the federal Toxic Substances Control Act. Ms. Grimaldi graduated from the University of California Hastings College of the Law magna cum laude and holds a Bachelor of Science Degree in Bacteriology from University of California, Davis. Prior to attending law school, she worked as a research assistant in laboratories at the University of California, San Francisco Cancer Research Institute and at the University of California, San Francisco School of Medicine.