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• Environmental Law Monitor, EPA, Litigation

The First Post-Preemption Roundup Trial Puts EPA’s Glyphosate Science Front and Center

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The U.S. Supreme Court on June 25 decided Monsanto Co. v. Durnell, 146 S. Ct. 2001 (2026), holding that the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), 7 U.S.C. § 136v(b), expressly preempts a state-law failure-to-warn claim that would require a cancer warning on a pesticide label that the U.S. Environmental Protection Agency (EPA) approved without one. The ruling removes the label-based warning theory that has driven much of the nationwide glyphosate docket, but it does not end the litigation.

The first Roundup trial to proceed since Durnell—Aretino et al. v. Bayer et al., No. 20SL-CC03676, pending in Missouri’s 21st Judicial Circuit (St. Louis County) — illustrates where the fight is moving. According to press reports of the trial, plaintiffs’ toxicology expert conceded on cross-examination that EPA’s December 2017 Revised Glyphosate Issue Paper found that the weight of the evidence does not support a glyphosate–cancer link, while plaintiffs continue to press allegations about ghostwritten science and regulatory influence.

For manufacturers, distributors, and insurers, the case signals that regulatory findings and the integrity of the regulatory record will be the central battleground in post-Durnell product liability litigation.

Key Legal Developments

  1. The Supreme Court’s Holding in Monsanto Co. v. Durnell

FIFRA’s uniformity provision bars states from imposing “any requirements for labeling or packaging in addition to or different from” those required under the statute. 7 U.S.C. § 136v(b). In Durnell, the court reasoned that federal law required Monsanto to sell Roundup with the label EPA approved at initial registration and repeatedly re-approved a label without a cancer warning. A Missouri tort judgment requiring such a warning would therefore impose a labeling requirement “in addition to” and “different from” Monsanto’s federal obligations, and the claim was expressly preempted.

Critically, the court treated EPA’s registration determination itself as a federal labeling requirement. It held that the agency’s conclusion that Roundup’s label need not carry a cancer warning “constitutes a federal labeling requirement that cannot be altered by state law, including state tort suits,” because registration decisions, like EPA regulations, “give content to FIFRA’s misbranding standards.”

  1. How Durnell Builds on Bates v. Dow Agrosciences

Durnell applies, rather than overrules, Bates v. Dow Agrosciences L.L.C., 544 U.S. 431 (2005). Bates held that § 136v(b) preempts only state labeling requirements that are not genuinely equivalent to FIFRA’s misbranding standards, and that state requirements must be measured against “any relevant EPA regulations that give content to FIFRA’s misbranding standards.” Bates illustrated the point with a claim that a label should have said “DANGER” rather than “CAUTION,” which would be preempted because a regulation, 40 C.F.R. § 156.64, assigns those signal words. Bates also held that claims that would not actually require relabeling — such as negligent manufacturing or testing, and breach of an express warranty — are not preempted.

Durnell extends the Bates “CAUTION/DANGER” example to EPA registration decisions. The court also drew on Bates’s distinction between efficacy claims, which EPA did not review at registration and which survived in Bates, and safety claims, which EPA thoroughly reviews at registration and which are therefore preempted.

  1. The Lower-Court Split That Durnell Resolved

Before Durnell, several appellate courts had rejected Monsanto’s preemption defense:

  • Hardeman v. Monsanto Co., 997 F.3d 941 (9th Cir. 2021), applied Bates’s two-part test and held that California failure-to-warn claims were consistent with FIFRA’s misbranding prohibition and thus neither expressly nor impliedly preempted.
  • Carson v. Monsanto Co., 92 F.4th 980 (11th Cir. 2024), held that neither FIFRA nor any other agency action imposed preemptive “requirements,” rejecting arguments based on EPA’s 2019 letter regarding California Proposition 65 warnings and on EPA scientific papers, including the 2017 Revised Glyphosate Issue Paper.
  • Johnson v. Monsanto Co., 333 Or. App. 678 (2024), found Hardeman and Carson well reasoned and held Monsanto’s FIFRA preemption arguments foreclosed.

These decisions focused largely on whether informal EPA statements carried the force of law. Durnell sidesteps that debate by locating the preemptive federal requirement in the registration and re-registration determinations themselves. Courts have already begun to recognize the shift: in Smith v. Superior Court, 121 Cal. App. 5th 607 (2026), the California Court of Appeal described Pilliod v. Monsanto Co., 67 Cal. App. 5th 591 (2021), as “abrogated on another ground” by Durnell.

  1. Subsequent History

The Supreme Court on June 30 granted certiorari in Monsanto Co. v. Anderson, 2026 U.S. LEXIS 2904, vacated the judgment of the Missouri Court of Appeals, Western District, and remanded for further consideration in light of Durnell. As noted above, California’s appellate courts have also treated earlier Roundup verdict decisions as abrogated in part. Additional remands and post-trial motions invoking Durnell should be expected.

  1. Parallel State Legislation

Several states have enacted statutes reinforcing the same principle. Georgia’s O.C.G.A. § 2-7-171 provides that, beginning January 1, 2026, an EPA-approved pesticide label, or one consistent with EPA’s most recent human health risk assessment, is a sufficient warning for state-law duty-to-warn purposes — subject to an exception where EPA determines the manufacturer knowingly withheld, concealed, misrepresented, or destroyed material health-risk information to obtain or maintain label approval. North Dakota’s N.D. Cent. Code § 28-01.3-11 contains a similar safe harbor tied to EPA labeling, risk assessments, and carcinogenicity classifications.

Regulatory Context: Glyphosate’s Registration History

Under FIFRA, no pesticide may be sold in the United States unless it is registered with EPA, and registration requires the applicant to submit extensive health and safety data and EPA to find that the product can be used without “unreasonable adverse effects on the environment.” 7 U.S.C. § 136a. Once a label is approved, a registrant generally may not modify it without submitting an application for amended registration and obtaining EPA approval. 40 C.F.R. § 152.44.

Glyphosate was first registered in 1974, re-registered in 1993, and was the subject of EPA’s comprehensive 2017 carcinogenicity evaluation. In the December 2017 Revised Glyphosate Issue Paper: Evaluation of Carcinogenic Potential, EPA’s Office of Pesticide Programs concluded that glyphosate is “not likely to be carcinogenic to humans.” Throughout this history, EPA has approved Roundup labels without a cancer warning — the very fact the Supreme Court found decisive in Durnell.

The 2017 paper now matters in two ways. First, it supports the federal labeling determination that preempts warning claims. Second, as the Aretino trial shows, it is a powerful cross-examination tool against causation experts on whatever claims survive preemption.

The Science/Regulatory Split

The litigation has long been defined by a divergence among scientific bodies. In 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans” (Group 2A) — a classification that plaintiffs have consistently used to argue that a cancer warning was required. By contrast, EPA’s 2017 assessment, and reviews by the European Chemicals Agency (ECHA) and the European Food Safety Authority (EFSA) as reported in coverage of the Aretino trial, did not find that glyphosate poses a cancer hazard to humans. The two sides frequently explain the difference as one of method: IARC evaluates whether a substance can cause cancer under some circumstances (hazard), whereas regulators assess risk at realistic exposure levels.

Courts have treated the split differently depending on the question presented:

  • After Durnell, the relevant inquiry is what EPA required on the label, not which scientific body is correct. An IARC classification does not alter the federal labeling requirement established by EPA’s registration decision.
  • Pre-Durnell force-of-law analysis. Courts such as Carson and Hardeman declined to give preemptive effect to EPA’s 2017 issue paper and 2019 letter because those documents lacked the formality and force of law. That line of reasoning is now of limited use for label-based warning claims.
  • Trial evidence. Where claims proceed, juries continue to hear both IARC and regulatory findings, and the weight given to each remains a matter for expert testimony and cross-examination — as the DeGrandchamp testimony in Aretino

State legislatures are also choosing sides. Georgia and North Dakota tie warning adequacy to EPA determinations, while some state regulatory regimes still reference IARC classifications for other purposes — for example: California Health & Safety Code § 111822 lists IARC Group 1, 2A, and 2B carcinogens among identified chemicals for purposes of that statute.

What This Means for Clients

  • Label-based warning claims face early dismissal. Manufacturers of EPA-registered pesticides should promptly evaluate pending failure-to-warn claims for dispositive motions grounded in Durnell and 7 U.S.C. § 136v(b), including in cases on appeal.
  • Expect plaintiffs to re-plead. Bates confirms that claims not requiring a labeling change — such as design defect, negligent manufacturing or testing, and express warranty — are not preempted on that basis. Plaintiffs will likely shift to these theories.
  • The regulatory record is now the battleground. Allegations of ghostwritten studies and improper relationships with agency officials, featured in Aretino, are likely to intensify as plaintiffs try to undermine the reliability of the EPA determinations that underpin preemption. Georgia’s statute already contains an exception for knowing concealment or misrepresentation found by EPA.
  • Document your regulatory submissions. Complete, well-documented FIFRA submissions and label-amendment histories are the foundation of a Durnell Registrants should ensure those records are organized and litigation-ready.
  • Insurers and downstream sellers should reassess reserves, coverage positions, and indemnity exposure in light of the narrowed universe of viable claims.

Conclusion

Durnell is a landmark win for pesticide registrants, confirming that EPA’s registration decisions set a uniform national labeling standard that state juries cannot override. But the Aretino trial shows the litigation is evolving rather than disappearing: the credibility of EPA’s science, and of the process that produced it, will now be tested in courtrooms on non-label theories. Companies operating in the agricultural chemical space should revisit their litigation strategies and regulatory records now.