The Supreme Court on Monday heard oral argument in Monsanto Company v. Durnell, a case on whether a company can be held liable under state law for failing to include a cancer warning on its product labels when the Environmental Protection Agency did not require such a warning and has concluded that the products in question are not carcinogenic.
The dispute centers on Monsanto’s popular line of Roundup herbicide products, whose main active ingredient is glyphosate. The Environmental Protection Agency first reviewed the safety of glyphosate-based pesticides in 1974 and has repeatedly concluded since then that glyphosate does not pose a public health risk. However, the EPA’s research has not dispelled claims that glyphosate exposure heightens cancer risk.
In 2015, a working group of the International Agency for Research on Cancer, part of the World Health Organization, broke with the EPA and top agencies in other countries by classifying glyphosate as “probably carcinogenic to humans.” Its report paved the way toward more than 100,000 lawsuits against Monsanto in the U.S. as Americans who had been diagnosed with non-Hodgkin’s lymphoma after using Roundup worked to hold the company liable for failing to warn them about the alleged cancer risk.
The case that’s now before the Supreme Court was brought by John Durnell in Missouri in 2019. Durnell contended that Monsanto was liable for damages under state law because it had not included a cancer warning on its Roundup product labels. Monsanto asserted, as it had in other cases across the country, that the Federal Insecticide, Fungicide, and Rodenticide Act, a federal law that regulates the use, sale, and labeling of pesticides, preempted Durnell’s lawsuit, both because FIFRA explicitly bars states from imposing additional or different labeling requirements on top of what’s required by federal law and because Monsanto could not have added a cancer warning without the EPA’s approval – approval that the company argued it would not have received because the agency has repeatedly concluded that glyphosate does not cause cancer.
The trial court in Missouri disagreed with Monsanto on preemption, and the jury went on to award Durnell $1.25 million in compensatory damages. In February 2025, the Missouri Court of Appeals affirmed this judgment, holding that Monsanto had failed to show both that Missouri’s requirements for product labels were at odds with federal law and that it had actually asked the EPA about adding a cancer warning to Roundup products. In January, the Supreme Court agreed to review this decision, which had deepened a split between lower courts over whether FIFRA allows state lawsuits like Durnell’s.
During approximately 75 minutes of oral argument on Monday, the justices wrestled with the structure and text of FIFRA, the EPA’s authority over Roundup product labels, and both express and implied preemption. Specifically, they considered whether FIFRA explicitly preempts lawsuits like Durnell’s through the statute’s uniformity provision, 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” by the EPA. And they also considered whether it implicitly preempts them because companies cannot change the safety warnings on their products in response to state requirements without the EPA’s permission.
Paul Clement, who argued on behalf of Monsanto, emphasized that “Congress plainly wanted uniformity when it came to the safety warnings on a pesticide label” and contended that allowing suits like Durnell’s undermines that goal. Clement highlighted the EPA’s in-depth assessment of products like Roundup and careful balancing of public safety, farmers’ needs, and economic interests, asserting that juries in states across the country cannot disregard or ignore the EPA’s guidance.
Justice Ketanji Brown Jackson pressed Clement on the pace of the EPA’s research, noting that 15 years typically passes between when a pesticide product – including its label – is first assessed and registered and when it is reassessed and reregistered. If new research about the safety of a product is released during that 15-year period, she asked, why can’t states play a role in ensuring that pesticide companies update their labels accordingly?
Similarly, Chief Justice John Roberts noted that states might be able to move faster than the EPA’s review process. In that situation, Roberts said, “it’s not necessarily the case that they’re doing something inconsistent with what EPA would do.” It could be that they’re responding to new safety information “more quickly than the federal government is.”
In his responses to both Jackson and Roberts, Clement urged the justices to see the pace of the EPA’s work as a feature, not a bug. “If the agency takes its time” reviewing new research, he said, it’s because “it’s charged with the responsibility of looking not just at sort of how the new information affects hazards and the like” but also whether the research is reliable. Indeed, Clement later noted, when the IARC released its glyphosate study in 2015, it was not as if the EPA “said we don’t want to hear about it.” The agency “exhaustively studied it and they actually did peer review that IARC doesn’t do. They looked at more sources than IARC did. And then they came to a conclusion that’s shared by regulators around the globe that glyphosate doesn’t have a cancer risk,” Clement said.
Clement further argued that a lawsuit over a pesticide product’s label is not the right way for states to support the EPA’s effort to keep product users safe. Instead, anyone concerned about the safety of a product on the market can “initiate a cancellation proceeding,” which prompts the EPA to reassess safety warnings.
Like Clement, Principal Deputy Solicitor General Sarah Harris, who argued on behalf of the federal government in support of Monsanto, emphasized that the EPA is not “just sort of sitting on its hands” and is, in fact, “monitor[ing] new information” that might reveal previously unknown safety risks. And when such information comes to light, Harris continued, the EPA’s response is “completely different from a state just saying slap a cancer warning on the product,” because the EPA is considering not just whether to add a warning, but whether a company should recommend different “protective gear” or whether the company should only be allowed to sell the product to “professional applicators” moving forward. The EPA, Harris explained, “is looking holistically not only at someone who might read the label and be exposed but also at other people in the process and endangered species,” and, under FIFRA, states can’t “try to sort of second-guess or undermine this process.”
As he did with Clement, Roberts asked Harris why states should not be able “to do something to call [newly identified] danger to the attention of the people while the federal government” goes through its review of the research. Harris responded that they can take action. Specifically, they “can petition for cancellation” to “spur EPA to action” or decide to “restrict the use” of a particular pesticide within state borders. What they can’t do, Harris said, is require new safety warnings on product labels.
Justice Neil Gorsuch questioned why states have the “greater power” to “stop the product from being sold at all” within their borders but not the “lesser power” of forcing changes to a pesticide’s label. Harris contended that Congress chose not to give them that power.
Ashley Keller, who argued on behalf of Durnell, contended that Monsanto is blurring an important distinction between the EPA’s registration authority under FIFRA and its authority to approve product labels. While the law makes clear that the agency will review proposed product labels in determining whether to approve a pesticide for sale and distribution in the U.S., FIFRA does not say, according to Keller, that a company can cite the EPA’s review of a label to fend off state-level misbranding lawsuits. “After two briefs and a lot of podium time, Monsanto still hasn’t pointed to one word in FIFRA’s text that” gives such weight to the EPA’s label assessment, he said.
Justice Elena Kagan asked Keller how allowing state-level challenges of product labels squares with FIFRA’s uniformity provision, which is “clearly designed to achieve uniformity in labeling.” Keller responded that, while it may be designed to achieve that, “that’s not the law Congress wrote,” and, as written, FIFRA does not prevent juries from determining that a pesticide product needed a different safety warning.
Justice Brett Kavanaugh pushed back against Keller’s answer, questioning how “uniformity” is satisfied by a situation in which “each state can require different things.” Keller again asserted that expressing a desire to have uniform labels is different than actually writing a law that requires that level of uniformity.
Keller faced notably fewer questions than Clement or Harris, which made it difficult to predict how the justices were leaning in the case.
The court’s decision is expected by early July.