Supreme Court Kills Most Roundup Cancer Lawsuits in 7-2 Ruling

The Supreme Court handed Bayer a sweeping legal victory Thursday, ruling 7-2 that federal pesticide law pre-empts most state-court cancer claims tied to Roundup, the widely used herbicide whose active ingredient is glyphosate. The decision in Monsanto v. Durnell effectively eviscerates thousands of lawsuits that plaintiff attorneys had filed in state courts alleging glyphosate caused cancer and that Bayer failed to warn consumers of the risk.

Justice Brett Kavanaugh wrote the majority opinion, anchoring it in the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), which gives the EPA authority to review and approve pesticides and explicitly bars states from imposing labeling or packaging requirements that differ from or add to what the agency requires. The EPA has re-evaluated glyphosate repeatedly over more than three decades and has consistently concluded it is not likely to cause cancer — meaning Monsanto is legally required to sell Roundup without a cancer warning unless and until the EPA changes course. Kavanaugh leaned heavily on the Court's 2008 Riegel decision, which found state tort claims pre-empted by a nearly identical clause in the Medical Device Amendments of 1976, calling that precedent 'dispositive.'

The dissent, written by Justice Ketanji Brown Jackson and joined by Justice Neil Gorsuch, argued that FIFRA's preemption clause should not block state claims where the alleged state-law violation is simultaneously a violation of FIFRA itself — specifically, that Roundup was 'misbranded' under federal law for lacking a cancer warning. Kavanaugh rejected that reasoning, warning it would effectively gut the EPA's authority over pesticide labels and only allow misbranding liability in the narrow scenario where EPA has already required a warning and the manufacturer ignores it.

The majority also pushed back on the dissent's claim that the ruling leaves injured plaintiffs without recourse, noting that affected parties can petition the EPA directly to modify, suspend, or cancel a pesticide's registration. The ruling lands as a significant blow to the mass tort litigation industry, which has extracted billions from Bayer in earlier settlements and verdicts despite the EPA's consistent safety conclusions on glyphosate.