Supreme Court Grapples with Roundup®, Federal Preemption, and the Limits of EPA Authority

On April 27, 2026, the U.S. Supreme Court heard oral argument in Monsanto Company v. Durnell, a closely watched case that could reshape the intersection of federal pesticide regulation and state tort law. At issue is whether failure to warn claims under state law, specifically those alleging that Roundup^® (the trade name for herbicide products containing the active ingredient glyphosate) should carry a cancer warning, are preempted by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). While the case centers on glyphosate, its implications extend far beyond a single product, raising fundamental questions about the role of U.S. Environmental Protection Agency (EPA) determinations, the scope of federal preemption, and the continued viability of state-law product liability claims.

Monsanto’s argument rests on a straightforward premise: FIFRA expressly preempts any state-law labeling requirements that are “in addition to or different from” federal requirements. According to Monsanto, state-law failure to warn claims fall squarely within that prohibition and are preempted. The company also advances an impossibility preemption argument. Because EPA approval is required before a pesticide label can be changed, Monsanto contends it cannot unilaterally add a warning label to prevent a failure to warn claim. In that scenario, complying with both federal and state requirements would be impossible, especially because in this case a cancer warning would be contrary to EPA’s repeated and current conclusion that glyphosate does not present a cancer risk to humans.

This framing positions the case as a direct descendant of PLIVA, Inc. v. Mensing and Mutual Pharmaceutical Co. v. Bartlett, where the Court found preemption when federal law constrained a manufacturer’s ability independently to alter warnings. The preemption argument was especially energized by the case Cipollone v. Liggett Group, Inc. — where federal cigarette labeling law required precisely what can be included on a cigarette pack label — and a state law imposing a cancer warning or other changes was not allowed.

Counsel for the respondent pushed back on a key premise underlying Monsanto’s position, that EPA registration decisions carry the force of binding federal “requirements.” Relying heavily on Bates v. Dow Agrosciences LLC, which ruled that FIFRA does not preempt state tort claims alleging that Dow’s herbicide damaged crops, the respondent argued that a pesticide may be federally registered yet still be “misbranded” under FIFRA. In other words, EPA approval is not dispositive of compliance. Crucially, the respondent emphasized that FIFRA’s statutory text treats EPA registration findings as only “prima facie evidence” of compliance, not as binding labeling mandates with preemptive force. From this perspective, state tort claims do not impose “additional” requirements but instead operate as parallel enforcement mechanisms, consistent with Bates.

Much of the argument focused on a familiar fault line in preemption jurisprudence: the distinction between cases where manufacturers can independently update warnings (Wyeth v. Levine) and those where federal law prohibits unilateral changes (PLIVA, Bartlett). The government, appearing as amicus in support of Monsanto, argued that FIFRA more closely resembles the latter. Unlike the U.S. Food and Drug Administration’s (FDA) “changes being effected” (CBE) process in Wyeth, EPA regulations require prior agency approval for all but very minor changes; changes to hazard warnings could not be made without prior agency approval. If the Court accepts that characterization, the case may turn less on statutory text and more on regulatory structure, specifically whether FIFRA leaves manufacturers with an ability to comply with warning obligations derivative of state-law theories of liability. The stakes are significant. A ruling in favor of Monsanto could:

• Substantially limit state-law failure to warn claims involving EPA-registered pesticides;

• Reinforce the primacy of federal regulatory determinations in product labeling; and

• Provide greater uniformity, and predictability, for regulated entities.

Conversely, a ruling for the respondent would:

• Preserve a major avenue of litigation risk through state tort law;

• Reinforce Bates as a meaningful constraint on preemption under FIFRA; and

• Potentially invite more aggressive state-level challenges to federally approved labels.

Beyond doctrine, the case reflects an ongoing policy debate: should federal regulatory requirements (in this case FIFRA) be the total, complex, encompassing regulatory requirements for use of a labeled pesticide under the law? If there is an unforeseen problem or an unacceptable risk with an approved FIFRA product following all necessary regulatory assessment procedures, FIFRA provided a remedy to address such a concern. Monsanto’s position aligns with a more centralized regulatory model, where EPA’s scientific determinations carry dispositive weight. The respondent’s approach, by contrast, preserves a role for juries and state law in second-guessing, or supplementing, those determinations. The Court’s decision may ultimately hinge on how it balances those competing visions.