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Monsanto Uses the Constitution to Challenge Warning Labels for Herbicide

Monsanto has, at least temporarily, lost its fight to avoid a Prop 65 warning label on its products containing glyphosate, a chemical used in the popular herbicide Roundup.  On January 27, 2017, a California judge tentatively dismissed Monsanto’s claims that the State of California unconstitutionally turned to an unelected, European organization to decide whether glyphosate posed a cancer risk.


Prop 65, also known as Proposition 65 or the Safe Drinking Water and Toxic Enforcement Act of 1986, was passed through California’s ballot initiative process in 1986 and codified in California’s Health and Safety Code. It prohibits businesses from releasing chemicals “known to the state to cause cancer or reproductive toxicity” into drinking water, and from exposing people to these chemicals without providing “clear and reasonable” warnings. The state publishes and frequently revises a “Prop 65 List” of chemicals covered by Prop 65’s warning label requirements. The list currently includes more than 900 chemicals.

In September 2015, California’s Office of Environmental Health Hazard Assessment (OEHHA) issued a notice of intent to list glyphosate as a Prop 65 chemical. That notice was based on a March 2015 report by the International Agency for Research on Cancer (IARC) that re-classified glyphosate as “probably carcinogenic to humans.” The IARC is a specialized agency that identifies as part of the World Health Organization. IARC uses this category when there is limited or inadequate evidence showing that a chemical causes cancer in humans, yet there is sufficient evidence demonstrating that the chemical causes cancer in animals.

The listing process at issue here—sometimes referred to as the Labor Code listing mechanism—involves the interplay of two code sections, one in the state’s Health and Safety Code and one in its Labor Code. OEHHA has interpreted these sections to require the agency to add any chemical IARC identifies as a carcinogen to the Prop 65 list.

The Lawsuit

On January 21, 2016, Monsanto petitioned for a review of the listing and sued OEHHA to prevent it from listing glyphosate as a Prop 65 chemical. Monsanto’s arguments invoked various constitutional provisions:

  • First, automatically listing IARC carcinogens as Prop 65 chemicals violates the “non-delegation doctrine” because it gives law-making power to IARC, an “unelected, undemocratic, unaccountable, and foreign body.”

  • Second, OEHHA’s listing process violates Monsanto’s due process rights because the listing process lacks safeguards and government oversight, and does not prevent against arbitrary action.

  • Third, the listing process violates the state Constitution because it gives IARC, a “private corporation,” power over the listing process.

  • Fourth, the listing process violates the Guarantee Clause of the U.S. Constitution, guaranteeing a “Republican Form of Government,” because it gives IARC, an unelected and unaccountable foreign body, law-making authority.

  • Fifth, Monsanto argued that giving IARC law-making power is a “radical change” to California government that requires a constitutional amendment.

  • Last, the listing violates Monsanto’s free speech because scientists at OEHHA had previously determined glyphosate was unlikely to cause cancer, and the warning would therefore require Monsanto to put a false or misleading statement on its product.

On January 27, 2017, the California Superior Court of the County of Fresno issued a tentative ruling dismissing the complaint. All of Monsanto’s claims were rejected:

  1. OEHHA has not unconstitutionally delegated law-making authority to IARC because the voters and legislature made the basic policy decisions about Prop 65, and IARC is an outside agency that does technical fact-finding but lacks law-making authority.

  2. There is no due process violation because due process does not apply to OEHHA’s listing process, which is a “quasi-legislative” act.

  3. There is no violation of the California Constitution because Monsanto did not allege facts showing IARC is a “private corporation.” The evidence shows it is an international agency formed by the World Health Organization, and the listing mechanism does not give IARC special power or privilege.

  4. Monsanto’s Guarantee Clause claim fails because the Guarantee Clause is enforced by Congress, not the courts.

  5. The argument that OEHHA’s interpretation of Prop 65 is a “radical change” requiring a constitutional amendment is a reframing of the unconstitutional delegation of power claim, which the court had already rejected.

  6. The free speech claim is premature, because Monsanto can still avoid Prop 65 labels if its products satisfy exceptions to Prop 65’s warning requirements.


Many regulatory agencies—including OEHHA and EPA—and scientists have previously determined that it is unlikely that glyphosate presents a cancer risk to humans. When the California state court’s ruling becomes final, it may be troubling for companies like Monsanto. While companies that make products including glyphosate will have 12 months to comply with Prop 65 warning requirements after the chemical is added to the Prop 65 list, a label may deter farmers and individuals from using products containing glyphosate. And other companies—in addition to Monsanto—that make products containing glyphosate will need to place cancer-related labels on their products or else face civil suits under Prop 65.

© 2022 ArentFox Schiff LLPNational Law Review, Volume VII, Number 48

About this Author

The Schiff Hardin Product Liability and Mass Torts Group comprises 40 lawyers — in New York, Washington, D.C., Chicago, Atlanta and San Francisco — solely devoted to helping clients face bet-the-company litigation against some of the most well-financed and formidable plaintiffs’ lawyers in the United States. Our lawyers try and win cases in some of the most plaintiff-friendly and inhospitable jurisdictions in the country, and when our clients ask us to create an exit strategy, we are equally adept at negotiating cutting-edge solutions to eliminate product liability and...