On April 27, the United States Supreme Court will hear oral arguments in Durnell v. Monsanto, a case brought by a Missouri plaintiff who alleges that exposure to the herbicide Roundup and its active ingredient, glyphosate, caused him to develop non-Hodgkin’s lymphoma. The case is one of thousands filed over the past decade against Monsanto Company (now owned by Bayer) by plaintiffs claiming that Roundup use caused cancer and that Monsanto failed to warn consumers of the risk. Bayer argues that these state law claims are preempted by federal pesticide law and should be dismissed. After years of litigation, that question is now before the Supreme Court, and its ruling could affect not only Roundup-related cases but also future lawsuits involving other pesticides.
Roundup is among the most widely used herbicides in the United States. Since the 1990s, it has been central to Monsanto’s “Roundup Ready” system, which pairs glyphosate-resistant seeds with herbicide application to allow spraying during growing seasons. Roundup has also been widely used in home and municipal landscaping.
Since 2015, tens of thousands of lawsuits have been filed against Bayer alleging that Roundup caused cancer. These cases are typically brought under state products liability law, particularly failure to warn claims. Bayer has consistently argued that such claims are preempted by federal law. Only a small number of cases have gone to trial, and outcomes have varied widely. Some juries have ruled in Bayer’s favor, while others have awarded plaintiffs damages exceeding $2 billion. Federal appellate courts are divided: the Third Circuit has held that federal law preempts these claims, while the Ninth and Eleventh Circuits have held that it does not.
The plaintiff in Durnell filed suit in Missouri state court in 2019. A jury found that Monsanto failed to warn him of potential health risks and awarded $1.25 million in damages. The Missouri Court of Appeals affirmed the verdict, rejecting Bayer’s preemption argument. The Missouri Supreme Court declined to review the case, bringing the matter to the U.S. Supreme Court.
At the center of the dispute is the Federal Insecticide, Rodenticide, and Fungicide Act (FIFRA), the primary federal law governing pesticide regulation. Under FIFRA, pesticides must be approved by the Environmental Protection Agency (EPA) before being sold or distributed. The EPA must determine that a pesticide will not cause “unreasonable adverse effects” on the environment, defined as risks to human health or the environment balanced against the product’s benefits. This evaluation includes assessing potential carcinogenicity.
FIFRA also defines the role of states in regulating pesticides. It prohibits states from imposing labeling or packaging requirements that are “in addition to or different from” federal requirements. It further bans the sale of “misbranded” pesticides, meaning products whose labels lack necessary warnings to protect health and the environment.
Failure to warn is a state law tort commonly raised in products liability cases. It does not allege that a product is defective, but that the manufacturer failed to provide adequate warnings or instructions. To succeed, a plaintiff must show both that warnings were insufficient and that the risk was known or reasonably knowable at the time.
The Supreme Court addressed FIFRA preemption once before in Bates v. Dow Agrosciences LLC. There, the Court held that state labeling requirements are preempted if they impose obligations “in addition to or different from” FIFRA. However, state law claims are not preempted if they are equivalent to and consistent with FIFRA’s prohibition on misbranding.
Bayer relies on Bates to argue that the plaintiff’s claim is preempted because it would effectively require adding a cancer warning to Roundup’s label. Bayer contends that complying with a state judgment would force it to alter federally approved labeling, which FIFRA prohibits.
The plaintiff argues the opposite, insisting that his claim parallels FIFRA’s misbranding provisions and is therefore not preempted. Citing Bates, he maintains that state law claims consistent with federal misbranding standards remain valid.
The case includes a notable twist. Unlike many similar lawsuits, the plaintiff bases his failure to warn claim not on product labels but on Monsanto’s marketing materials from the 1990s and 2000s. He alleges that advertisements portrayed Roundup as completely safe, showing users applying it in shorts and tee shirts. Because FIFRA governs labeling rather than marketing, the plaintiff argues that his claim falls outside the scope of federal preemption.
Bayer disputes this distinction, asserting that regardless of how the claim is framed, resolving it would still require changes to product labeling, bringing it within FIFRA’s preemptive scope.
At this point, it is difficult to predict how the Supreme Court will rule. An amicus brief from the Office of the Solicitor General supports Bayer’s position, while advocacy groups such as the Make America Healthy Again movement back the plaintiff. Whatever the outcome, the Court’s decision is likely to have far-reaching consequences, shaping pesticide regulation and influencing thousands of ongoing and future cases.
Rollins, Brigit. “Durnell v. Monsanto: Pesticide Liability at the Supreme Court.” Southern Ag Today 6(17.5). April 24, 2026. Permalink
