Supreme Court Vacates $28 Million Roundup Verdict Against Monsanto

The U.S. Supreme Court on Tuesday tossed a $28 million judgment against agricultural biotech company Monsanto, casting deep doubt on the future of lawsuits claiming the herbicide Roundup lacked proper cancer warnings.

The justices granted Monsanto’s petition, vacated a California appellate court ruling that had upheld the award, and sent the case back to state judges for reconsideration. The move follows a significant federal ruling from earlier this year that restricted product liability claims brought under state warning laws.

A Reduced Jury Award Followed by Years of Appeals

The California case began in 2021, when Carlsbad resident Mike Dennis sued Monsanto, which was acquired by Bayer, in San Diego Superior Court. Dennis alleged that exposure to Roundup caused him to develop mycosis fungoides, a rare form of non-Hodgkin lymphoma. His lawsuit claimed the manufacturer knew the weedkiller carried cancer risks but sold it without adequate warnings in violation of California law.

A jury originally found Monsanto liable and awarded Dennis $332 million, including $7 million in compensatory damages and $325 million in punitive damages. Although the trial judge refused Monsanto’s request for a new trial, the court reduced the punitive damages to $21 million in 2024 after finding the original sum unconstitutionally excessive. Monsanto appealed, arguing that the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) preempted the failure-to-warn claims, but a California appeals court affirmed the verdict in November 2025.

Precedent Established in a Similar Missouri Lawsuit

The Supreme Court’s decision to intervene came after it decided a nearly identical case from Missouri. In that matter, farmer John Durnell sued Monsanto and Bayer in 2019, alleging the companies failed to warn him of cancer risks that led to his non-Hodgkin lymphoma. A Missouri jury awarded Durnell $1.25 million in 2023, and a state appellate panel upheld the award.

The high court heard oral arguments in April and issued a 7-2 ruling in June in favor of Monsanto. Writing for the majority, Justice Brett Kavanaugh stated that the Environmental Protection Agency had repeatedly approved Roundup labels without cancer warnings and determined the product does not cause cancer. Because federal law requires herbicide labels to remain uniform across the country, state laws cannot demand different wording. Kavanaugh wrote that “FIFRA therefore expressly preempts Durnell’s claim.” Justices Ketanji Brown Jackson and Neil Gorsuch dissented.

What the Decision Means for Consumers and Injury Claims

The high court’s action effectively halts the $28 million California award and directs the state appellate court to revisit the case under the federal preemption standard. A Monsanto spokesperson said the company will urge the California appellate panel to vacate the trial verdict completely. Legal representatives for Dennis could not be reached for comment.

For consumers and agricultural workers, the ruling likely closes future paths for state-law failure-to-warn lawsuits involving Roundup. When a federal agency approves a uniform product label that omits a health warning, plaintiffs may no longer rely on state warning laws to challenge that packaging in court.

Navigating the boundary between federal regulations and state personal injury laws can be complex. When product labeling rules and severe illnesses intersect, consulting an experienced personal injury attorney can help injured individuals evaluate what legal avenues remain available.

This article is general information based on Courthouse News Service and court or agency records available at publication time. It is not legal advice; laws and deadlines differ by state and by case. Published October 13, 2026.