By Patrick Thomas and Lydia Wheeler
The Supreme Court grilled Bayer over whether it is liable for failing to warn consumers that its flagship weedkiller Roundup might cause cancer, in a case that could wipe out thousands of legal claims and help bring closure to a battle that has engulfed the company for years.
Justices across the ideological spectrum on Monday appeared receptive to arguments that the pharmaceutical and agriculture company can be sued for damages under a Missouri law requiring companies to warn consumers about risks from their products, even though the product wasn't mislabeled under federal law because regulators had determined it was safe to use.
A ruling against Bayer would be a blow to the company's efforts to contain the Roundup litigation, which has cost it billions of dollars.
Chief Justice John Roberts expressed openness to Bayer's argument that federal law is designed to create uniformity in the labeling of herbicides. But he questioned why states would be unable to do anything if a product is determined to be dangerous after the government approved its use.
If it turns out the states were right, "it might've been good if they had an opportunity to do something to call this danger to the attention of the people while the federal government was going through its process, " he said.
Bayer has been wrapped up in litigation over Roundup -- the world's most widely used weedkiller -- since its $63 billion acquisition of Monsanto in 2018. Monsanto revolutionized American agriculture by developing the powerful herbicide.
Thousands of consumers have sued the company over almost a decade claiming glyphosate, the key ingredient in Roundup, caused their cancer, and that the company should have done more to warn them about the risks.
The case that Bayer petitioned the Supreme Court to take on involves a Missouri gardener, John Durnell, who used the weedkiller for years. He alleges exposure to it caused him to develop non-Hodgkin lymphoma and that the company failed to warn of any danger on the product label. A jury awarded him $1.25 million in damages, which were upheld by a state appeals court.
Getting a favorable ruling from the Supreme Court is a key part of Bayer Chief Executive Bill Anderson's plan to contain the Roundup litigation this year. If Bayer prevails, it could help lead to the dismissal of thousands of cases against the company. Some plaintiffs could refile but it would also eliminate a key argument about the company's failure to warn, making it potentially more difficult for them to win at trial.
Bayer has maintained that Roundup is safe to use. Governments globally and the Environmental Protection Agency in the U.S. have repeatedly determined that glyphosate isn't likely to be carcinogenic in humans and approved Roundup labels that didn't include cancer warnings. The World Health Organization's International Agency for Research on Cancer, however, classified glyphosate as "probably carcinogenic to humans" in 2015.
Durnell and other plaintiffs argue the company should go further in how it warns farmers and landscapers of the risks the herbicide may pose. But Bayer argues that those claims supersede the EPA's authority and would cause a patchwork of rules imposed by individual states.
The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) prohibits states from imposing different or additional warnings from those required under the federal law.
States do have the authority to pull a product from the marketplace in their region, and Justice Neil Gorsuch questioned why they can't also punish companies for failing to warn consumers about the dangers.
"That greater power exists, why doesn't the lesser power," he said.
The Trump administration supported Bayer's appeal, arguing the company can't be held liable for failing to warn consumers because the EPA approved Roundup's label without a warning and the company isn't free to add one without the agency's approval.
Durnell's lawyer, Ashley Keller, said both state and federal law have to be followed. But Justice Brett Kavanaugh pushed back on that. "If the label is illegal in one state and legal in another state, that's uniformity?" he asked.
Write to Patrick Thomas at patrick.thomas@wsj.com and Lydia Wheeler at lydia.wheeler@wsj.com
(END) Dow Jones Newswires
April 27, 2026 14:32 ET (18:32 GMT)
Copyright (c) 2026 Dow Jones & Company, Inc.
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