On June 22, 2020, Judge William Shubb of the US District Court for the Eastern District of California entered an order prohibiting the State of California from requiring Prop 65 warnings for glyphosate, the active ingredient in the herbicide Roundup®. The decision was not based on whether glyphosate had been improperly listed under Prop 65, or whether the amount of exposure to average users was below the no significant risk level. Rather, the court concluded that the warnings were prohibited under the US Constitution’s First Amendment as compelled government speech. This decision is important, as it is the first final court ruling to find that the state cannot compel a warning communicating that a chemical is “known to cause cancer” when that warning is not “factual and uncontroversial.”


The carcinogenicity of glyphosate has been studied by regulators around the world, including the EPA, European Commission, World Health Organization, and the governments of Germany, Canada, Australia, New Zealand, Japan, and South Korea. Until 2015, the unanimous view of the regulators was that there was insufficient or no evidence that glyphosate causes cancer. That year, however, the International Agency for Research on Cancer (IARC) issued a monograph that classified glyphosate as “probably carcinogenic” to humans based on “sufficient evidence” that it caused cancer in experimental animals and “limited evidence” that it could cause cancer in humans. Under Prop 65’s “Labor Code” mechanism, this monograph led to a listing for glyphosate in July 2017, notwithstanding the continued conclusion of USEPA that glyphosate was not carcinogenic.

A challenge to that listing was rejected by the California Court of Appeal. No other regulator has followed IARC, and, in August 2019, EPA sent a letter to companies that had registered glyphosate under federal law, stating that “EPA considers the Proposition 65 warning language based on the chemical glyphosate to constitute a false and misleading statement,” and products containing the Prop 65 warning on their labeling were considered “misbranded” under federal law.

The lawsuit

In November 2017, Monsanto and a group of farming associations filed a complaint seeking to enjoin the state from enforcing Prop 65 warnings for glyphosate under first amendment, preemption, and due process theories.  See National Association of Wheat Growers et al. v. Zeise, E.D. Cal. No. 2:17-cv-02401 (filed November 15, 2017).

On February 26, 2018, Judge Shubb issued an order granting the plaintiffs’ motion for preliminary injunction, finding that the state could not compel Prop 65 warnings for glyphosate consistent with the First Amendment. The case proceeded to cross-motions for summary judgment, with the court issuing its opinion on June 26, 2020.

The court prohibits a Prop 65 warning that is neither factual nor uncontroversial

The court assessed the viability of Prop 65 warnings under existing Supreme Court authority regarding compelled commercial speech. That authority holds that a state may compel commercial actors to disclose “purely factual and uncontroversial information,” as long as the disclosures are “reasonably related” to a substantial government interest and are neither “unjustified [n]or unduly burdensome.” Unlike Prop 65’s burden shifting, a First Amendment claim requires the government to bear the burden of proof on these issues.

Judge Shubb found that the Prop 65 safe harbor warning, as well as several alternative warnings proposed by the Attorney General, were misleading as applied to glyphosate. “Notwithstanding the IARC’s determination that glyphosate is a ‘probable carcinogen,’ the statement that glyphosate is ‘known to the state of California to cause cancer’ is misleading. Every regulator of which the court is aware, with the sole exception of the IARC, has found that glyphosate does not cause cancer or that there is insufficient evidence to show that it does.”

Judge Shubb further noted that the State was not without recourse to further its interest in informing Californians about exposures to chemicals that cause cancer, consistent with the First Amendment. “California has options available to inform consumers of its determination that glyphosate is a carcinogen, without burdening the free speech of businesses, including advertising campaigns or posting information on the Internet.”

The court issued a permanent injunction, prohibiting enforcement of Prop 65’s warning requirement for exposures to glyphosate by the Attorney General and all persons and entities in privity to him, presumably covering private enforcers, who have been found to have sufficient privity to each other in serial Prop 65 enforcement actions, and are subject to Attorney General oversight.

Next steps?

Presumably, the Attorney General will appeal this ruling to the Ninth Circuit. That court has been no stranger to litigation over compelled commercial speech under the First Amendment, having most recently issued an opinion finding the City of Berkeley’s required warning about exposure to radiation from cell phones to have imposed an unreasonable burden under the First Amendment. And, given the U.S. Supreme Court’s renewed interest in First Amendment jurisprudence, it is not out of the realm of possibility that this case will land there at some point. We assume the last chapter has yet to be written in this story.