Updated April 27, 2026 at 6:48 PM EDT
A divided U.S. Supreme Court on Monday heard a dispute over labels on the popular Roundup weed killer, which thousands of people blame for their cancers.
How the Supreme Court rules could have implications for tens of thousands of lawsuits against Roundup maker Monsanto, which is now owned by Bayer. The case centers on who decides about warning labels on chemicals: the federal government — or states or juries.
The main plaintiff in Monday's case is John Durnell. Durnell in 2019 sued Monsanto in a state court in Missouri, alleging he contracted non-Hodgkin's lymphoma because of his 20-year exposure to glyphosate, a chemical included in the weed killer. Durnell regularly sprayed the weed killer throughout his neighborhood.
A jury sided with Durnell on his claim that Monsanto had failed to properly warn users about risks, awarding him more than $1 million in damages.
Missouri law bans the sale of dangerous pesticides that lack an "adequate warning," Durnell's lawyer Ashley Keller wrote. Keller says the key questions are for juries to decide.
Durnell is one of tens of thousands of people to sue because they say they faced harm because of Roundup. Those plaintiffs have experienced mixed success in the lower courts.
Monsanto argues those claims should have been preempted by the Federal Insecticide, Fungicide, and Rodenticide Act, which requires manufacturers to register pesticides with the EPA before selling them, which Monsanto did. The EPA also signs off on labels for those pesticides.
Paul Clement, a former solicitor general and a lawyer for Monsanto, argued that it's important to have a uniform standard nationwide.
"It's probably the most like studied herbicide in the history of man and they've all reached the conclusion, based on more data and the kind of expert analysis they can do, that there isn't a risk here," he told the justices. "You shouldn't let a single Missouri jury second guess that judgment."
The justices will not be evaluating whether glyphosate causes cancer. Rather, they'll consider who should decide what appears on warning labels and whether states have a role to play after the EPA weighs in.
The current U.S. solicitor general backed Monsanto. Sarah Harris, his principal deputy, said the Environmental Protection Agency is in the driver's seat, not anyone in Missouri.
"Missouri thus requires adding cancer warnings but federal law requires EPA to approve new warnings and tasks EPA with deciding what label changes would mitigate any health risks," Harris argued. "State law must give way."
Several justices, including Brett Kavanaugh, appeared to agree with Monsanto's argument about the need for a single, uniform standard across the country.
But others, like Chief Justice John Roberts, wondered what would happen if the federal government moved more slowly than states did, who wanted to act quickly on information about new dangers.
"Well, it does undermine the uniformity," Roberts said. "On the other hand, if it turns out they were right, it might have been good if they had an opportunity to do something, to call this danger to the attention of people while the federal government was going through its process," he said about states.
Justice Ketanji Brown Jackson asked about the emergence of new science, and the EPA's reviews.
"There's a 15-year window between when that product has to be re-registered again and lots of things can happen in science, in terms of development about the product," she said.
Bayer, which now owns Monsanto, only sells Roundup that contains glyphosate to farmers and businesses these days. Bayer has been pushing to resolve scores of the residential cases through a sweeping settlement, trying to put the costly claims behind it.
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