During oral argument on Monday in Monsanto Company v. Durnell, the justices will consider a question that might seem quite dry: Does the federal law governing pesticide product labels supersede state labeling requirements? This is not your average Supreme Court case, however. Rather, it thrusts the court into a battle involving over 100,000 lawsuits, “billions and billions” of dollars, the international scientific community, federal and state policymakers, and, if you ask Monsanto, the very future of U.S. agriculture and innovation.
But we’ll get to all that. First, let’s talk about Roundup weedkiller.
Roundup is a popular line of herbicide products manufactured and distributed by Monsanto. Its main active ingredient is glyphosate, which is used around the world to kill weeds without harming crops. Glyphosate “is so effective,” according to one pesticide expert, “that it is estimated to have saved farmers a staggering ‘$21 billion’ annually.”
The Environmental Protection Agency first reviewed and registered glyphosate-based pesticides in 1974. Since then, it has regularly evaluated the safety of these products and investigated whether glyphosate exposure causes cancer, concluding each time that it does not pose a public health risk. Over the same period, the EPA has repeatedly approved Roundup product labels that did not include a cancer warning.
However, in 2015, a working group of the International Agency for Research on Cancer, part of the World Health Organization, came to a different conclusion. After conducting a broad review of research on links between glyphosate and cancer, it classified the herbicide as “probably carcinogenic to humans.”
The IARC’s report set in motion a “tidal wave of litigation” against Monsanto as Americans who had been diagnosed with non-Hodgkin’s lymphoma after using Roundup sought to hold the company liable for failing to warn them about the potential risks of glyphosate exposure. One such lawsuit was filed by John Durnell in Missouri in 2019, and it is his lawsuit that is now in front of the Supreme Court.
Before the trial court, Durnell, who believes that Roundup use caused him to develop cancer, argued that Monsanto was liable under Missouri law for defective design, failure to warn, and negligence. Monsanto countered – as it had done in related lawsuits across the country – that he could not bring any of those claims because state rules for pesticide labels are preempted by the Federal Insecticide, Fungicide, and Rodenticide Act, a federal law that regulates the use, sale, and labeling of pesticides. Specifically, the company pointed to the part of FIFRA that addresses state authority, which says that states “shall not impose or continue in effect any requirements for labeling or packaging in addition to or different from those required” under federal law, and it emphasized that the EPA had not required it to include a cancer warning on Roundup labels.
The trial court denied Monsanto’s motions for a directed verdict in its favor, and the jury went on to side with Durnell on the failure-to-warn claim, awarding him $1.25 million in compensatory damages.
In February 2025, the Missouri Court of Appeals affirmed the judgment, holding that Monsanto had failed to show that Missouri’s labeling rules are at odds with FIFRA’s rules. “The record contains no evidence that Monsanto either informed the EPA of the justifications for a change to its warning label or that the EPA has informed Monsanto it would not approve such a warning,” the court explained. According to the court, it is not enough to argue, as Monsanto did, that “the regulatory history of glyphosate constitutes ‘clear evidence’ the EPA would not approve a cancer warning on Roundup’s label.”
After the Missouri Supreme Court declined to weigh in, Monsanto turned to the Supreme Court, noting that the Missouri Court of Appeals’ decision had deepened a disagreement involving both other state courts and federal courts of appeals over whether states can require warnings about glyphosate when the federal government does not. In an amicus, or “friend of the court,” brief filed at the Supreme Court’s request, U.S. Solicitor General D. John Sauer urged the justices to take up the case and offered support for Monsanto’s position. In January, the court added the case to its oral argument docket.
In its brief on the merits, Monsanto contended that lawsuits like Durnell’s are both expressly and impliedly preempted by FIFRA. The federal law expressly, or explicitly, bars such state claims, according to the company, by declaring that states cannot impose label requirements “in addition to or different from” federal requirements. And it impliedly, or implicitly, preempted these suits because, under FIFRA, Monsanto cannot add a cancer warning to its product labels without the EPA’s approval, and the EPA “has determined—repeatedly—that glyphosate does not cause cancer in humans.” Moreover, the company noted that the EPA has directly reviewed the IARC’s findings, examining “all relevant evidence IARC collected, and numerous studies IARC failed to consider.” The agency “concluded that ‘[t]he strongest support’ was for classifying glyphosate as ‘not likely to be carcinogenic to humans.’”
It defies both “Congress’ will and common sense,” Monsanto continued, to allow “lay juries” in states across the country to reject EPA’s extensive research when considering lawsuits over the product labels it has approved. Congress carefully crafted FIFRA to ensure that the agency had the authority “to evaluate health risks and decline to register pesticides that lack necessary health warnings.” In doing so, the EPA “strike[s] a balance” between educating the public about potential health risks and promoting pesticide use and development in the service of strengthening the food supply. Suits like Durnell’s threaten that balance, Monsanto contended, adding that “[t]he threat is not just to existing products, but to the incentives to develop the next generation of even better pesticides.” “[T]here is no such thing as a no-risk pesticide. And if the ultimate result of exhaustive research-and-development efforts is equally exhaustive state-court litigation under the varying laws of 50 states, then the whole game is not worth the candle.”
In a friend-of-the-court brief filed after the Supreme Court agreed to take up Monsanto’s case, the federal government (which will also be arguing before the court) again supported Monsanto’s position, asserting that FIFRA’s uniformity requirement clearly bars states from requiring cancer warnings on labels that the EPA does not require. To hold otherwise, Sauer wrote, would be to create a “State-by-State cacophony.” “If States can compel” Monsanto “to add a cancer warning—contrary to EPA’s scientific judgments—States could drown EPA’s approved warnings in a sea of local health and environmental concerns.”
In his brief on the merits, Durnell acknowledged that the EPA has significant authority under FIFRA to review and register pesticides for sale and distribution in the U.S. The law instructs judges to defer to the EPA’s registration decisions if the agency shows its decisions were “based on substantial evidence.” However, Durnell contended, this registration authority does not give the EPA “ultimate power” over pesticide labels. While FIFRA makes it clear that the agency should consider a product’s label during the registration process, it does not say that its label assessments must be accepted in courtrooms nationwide. “There is … no provision of FIFRA that requires judges or juries to defer to the Administrator’s determination that a pesticide complies with (or violates) the misbranding prohibition,” Durnell said.
Durnell further argued that Missouri’s effort to hold manufacturers accountable for failing to warn customers about health risks is consistent with FIFRA’s misbranding prohibition and thus does not run afoul of the portion of the law that prevents states from “impos[ing] any requirements for labeling or packaging” that add to or differ from federal requirements. “State law forbids the sale of a pesticide without a truthful and ‘adequate warning.’ Federal law prohibits selling a pesticide with a misleading or ‘inadequate warning[].’ Barring an outright copy-and-paste, it would be hard to have less daylight escape between the legal standards established.” Those similarities are what matter here, Durnell emphasized, not the jury’s and the EPA’s contrasting conclusions about the health risks posed by glyphosate.
In its reply brief, Monsanto described Durnell’s argument as a “remarkable submission” that “is flawed on multiple levels.” Because Congress intended “to ensure ‘uniformity’ in labeling,” the court should not hold “that pesticide manufacturers have no way to know whether a pesticide is misbranded until they see what comes out of a particular jury box,” the company wrote.
As noted above, Monday’s argument in Monsanto Company v. Durnell will take place against the backdrop of a much broader battle over the future of Monsanto and, indeed, of glyphosate. In February, President Donald Trump issued an executive order on glyphosate, which stated that its continued production and use are critical to national security. That same month, Monsanto’s parent company, Bayer, announced a proposed $7.25 billion settlement aimed at resolving “current and future cancer lawsuits over its Roundup weedkiller,” including lawsuits that would be foreclosed by a Supreme Court ruling in Monsanto’s favor. Experts have noted that the settlement agreement would soften the blow for Monsanto if the Supreme Court rules against it and do the same for its challengers if a majority reaches the opposite result.
The Supreme Court’s decision is expected by early July.