Bayer, the multinational biotech conglomerate that owns Monsanto, which manufactures Roundup, scored a major victory on Thursday over people suing the company for not including a warning about cancer risks on the weedkiller’s label. In a 7-2 decision, the U.S. Supreme Court overturned a state court decision from Missouri, and effectively blocked thousands of other lawsuits alleging Bayer was civilly liable for failing to warn users that glyphosate, the active ingredient in Roundup, is a carcinogen.
Bayer insists glyphosate does not pose a cancer risk to those who use Roundup or are exposed to it. The EPA does not classify glyphosate as a likely carcinogen, but the World Health Organization’s International Agency for Research on Cancer classified the chemical as “probably carcinogenic to humans” in 2015.
Bayer paid over $10 billion to settle more than 95,000 lawsuits filed over Roundup’s label not warning users about the risk of cancer in 2020. Approximately 200,000 claims over Roundup causing cancer have been filed against Monsanto, which Bayer bought in 2018. Most of those claims were from home users of Roundup. In 2021, Bayer announced it would remove glyphosate from the lawn and garden versions of Roundup. The company did not reformulate Roundup for agricultural uses, although it said it might have to pull its product from the U.S. market if it kept being sued.
The lawsuits against Bayer over Roundup have been filed at the state level and relied on state laws about a company’s responsibility for informing about health risks from its products. In recent years, Bayer has conducted an extensive lobbying campaign aimed at getting state legislature to grant it greater legal protection against lawsuits by passing bills that require warning labels for pesticide and herbicides to only list the health risks recognized by the EPA.
In 2015, the Iowa Senate passed a Bayer-backed bill creating such legal protection. Appearing on Iowa Press at the beginning of that year’s legislative session, Senate President Amy Sinclair, a Republican from Allerton, characterized lawsuits over Roundup not warning users about cancer risks as a “money grab, and it’s a money grab on a business where all they are doing is following the letter of the federal law and that shouldn’t be allowed.”
Strong public pushback against the bill helped prevent it from advancing in the Iowa House, and it died. “In 2025, according to client reports published by the state, Bayer paid lobbyists [at the Iowa Capitol] $123,250. Reports for 2024 [when a Bayer-backed bill was introduced, but failed to advance] show $86,099 spent,” Iowa Capital Dispatch reported. “Between 2021 and 2023, years before the pesticide labeling bill was introduced, Bayer spent annually between $20,000 and $30,000 on its lobbying efforts.”
The Trump administration has been very supportive of Bayer and glyphosate. In February, against a backdrop of growing state-level lawsuits over Roundup, President Trump took the extraordinary step of using the Defense Production Act of 1950 to designate the production of glysophate as national security priority. The designation provides substantial protection against lawsuits for the manufacture and sale of glyphosate. Trump’s order said “glyphosate-based herbicides are a cornerstone of this Nation’s agricultural productivity and rural economy, allowing United States farmers and ranchers to maintain high yields and low production costs while ensuring that healthy, affordable food options remain within reach for all American families.”
Only Bayer, through Monsanto, makes glyphosate. All Bayer’s glyphosate is formulated at a plant in Muscatine, before it is shipped to a plant in Luling, Louisiana, where the manufacturing process is finished.
Monsanto v. Durrell, the case the Supreme Court decided on Thursday, was filed by John Durrell, a St. Louis resident who was diagnosed with non-Hodgkin’s lymphoma, a cancer common among litigants in Roundup lawsuits. Known as the “spray guy,” Durrell had spent 20 years applying to Roundup in local parks on behalf of his neighborhood association. Durrell sued Monsanto in 2019 for “failure-to-warn” by not including information about possible cancer risks on Roundup’s label. In 2023, a civil jury found in Durrell’s favor and awarded him $1.25 million.
Bayer appealed the ruling, claiming that the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) overrides state laws, and unless the EPA mandates a herbicide or pesticide display a cancer warning, a company isn’t required to do so.
In 2025, the Missouri Court of Appeals rejected Monsanto’s appeal. The company appealed directly to the U.S. Supreme Court. The U.S. Department of Justice filed an amicus curiae brief supporting Monsanto.
In his opinion for the majority, Justice Brent Kavanaugh wrote that “FIFRA expressly preempts Durnell’s claim” and ruled that states cannot impose labelling requirements different from those established by the EPA.
“In accepting Monsanto’s argument and holding that Durnell’s failure-to-warn claim is preempted, the Court misunderstands FIFRA’s requirements, misinterprets the scope of FIFRA’s preemption, and ultimately leaves Durnell without a remedy for the significant harms he has suffered,” Justice Ketanji Brown Jackson wrote in dissent.
“FIFRA expressly limits States’ authority to regulate pesticide labels, but it does not eliminate that authority,” Jackson agreed; however, she said states still retain authority equal to the federal government to “require a pesticide manufacturer to adequately warn users of the potential dangers of using its product.”
Jackson, the only justice appointed to the court by President Biden, was joined in dissent by Neil Gorsuch, one of President Trump’s appointees.
“This decision is good for American farmers who help feed the world,” Bayer CEO Bill Anderson said in a statement after the court handed down its decision. “It provides the regulatory clarity necessary for innovators like us to develop the agricultural tools that guarantee an affordable food supply.”
The Iowa Farmers Union (IFU) issued a statement calling the court’s decision “a huge step backwards.”
“The path to safe and effective pesticides is not to give blanket protections to pesticide manufacturers,” IFU President Aaron Lehmann said, “Iowa’s leading cancer rate won’t go down when multi-national manufacturers of pesticides are given a free pass for their products that have proven links to cancer.”
Both candidates for governor issued statements denouncing the decision.
“This is not a win for farmers – in any way,” Republican Zach Lahn said. “Farmers have now lost their ability to have recourse when they are harmed by these products… Civil liability is a key part of the free market and that has now been taken away to the detriment of the people.”
Democrat Rob Sand said, “The decision is wrong, gross, and will continue to make life worse for Iowans.”
“Government insiders here in Iowa have already tried to grant immunity for companies poisoning Iowans with cancer-causing chemicals. My position is clear: no immunity for chemical companies sickening Iowans.”
Neither Lahn nor Sand served in the Iowa Legislature, but Lahn’s running mate, Derek Wulf, was a member of the Iowa House in 2024 and 2025 when Bayer was pushing for a bill to limit its legal liabilities. When Lahn announced his pick for lieutenant governor earlier this month, journalist Laura Belin reported that Wulf was listed as one of the legislators backing the Bayer bill in a 2025 ad by the Modern Ag Alliance, a lobbying group founded by Bayer.
“Wulf has never stated that he supported this legislation,” a Lahn campaign spokesperson told Belin.
Wulf made no public statement about the Bayer bill when it was before the legislature.
In a later statement, the Lahn campaign told Belin, “[Wulf] does not support blanket immunity, and has never voted for blanket immunity.”
Because the Bayer bill failed to advance in the Iowa House, Wulf never had the opportunity to vote on it.
