The U.S. Supreme Court has handed Monsanto one of its most consequential corporate liability wins by upholding a defense against state court claims that Roundup caused cancer without adequate warnings.
In the case Monsanto Company v. Durnell, issued Thursday, the Court ruled 7-2 that Missouri’s jury verdict requiring Monsanto to add a cancer warning to Roundup would violate federal law. The decision narrows the path for thousands of Americans who allege glyphosate-based weedkillers caused their cancers and should have carried such warnings.
The ruling also reveals an unusual alignment between President Donald Trump’s Department of Justice and the Environmental Protection Agency, which both defended Monsanto’s argument that state courts cannot impose labeling requirements beyond what federal law mandates. Both agencies contended that because the EPA had approved Roundup’s label without a cancer warning, states could not require one.
The case began in 2019 when John Durnell, a Missouri man, sued Monsanto after using Roundup for two decades and developing non-Hodgkin’s lymphoma. A jury found Monsanto liable for failing to include a cancer warning and awarded him $1.25 million.
Monsanto appealed on the grounds that federal pesticide law preempts state claims. The Court agreed in a 7-2 decision, with Justice Brett Kavanaugh writing the majority opinion and Chief Justice John Roberts joining as well as Justices Clarence Thomas, Samuel Alito, Sonia Sotomayor, Elena Kagan, and Amy Coney Barrett.
The ruling held that any state court requirement for a cancer warning would be “in addition to or different from” federal labeling requirements under FIFRA (the Federal Insecticide, Fungicide, and Rodenticide Act). By so holding, the Court deemed such state claims preempted.
Justice Ketanji Brown Jackson dissented, joined by Justice Neil Gorsuch. She argued that Durnell’s claim was not “in addition to” federal law but rather “equivalent to FIFRA’s key labeling requirement.” Jackson also criticized the majority for misreading FIFRA and converting agency approval into a liability shield.
The decision has significant implications for consumers who have filed lawsuits claiming Roundup caused harm. With over 65,000 active lawsuits nationwide, the ruling puts millions of claims at risk.
Jackson highlighted concerns about the EPA’s handling of glyphosate, particularly its failure to apply a child-protective tenfold safety margin since 1998.