If the courts defer to regulators, who ensures the regulators keep pace with evolving science?
The US Supreme Court handed Monsanto a sweeping legal victory this week, ruling 7–2 that Americans can no longer pursue many state-law failure-to-warn claims against the company over the absence of a cancer warning on Roundup labels.
The case, Monsanto Co. v. Durnell (decided 25 June 2026), was brought by John Durnell, a Missouri man who used Roundup for roughly 20 years and developed non-Hodgkin’s lymphoma. A jury awarded him over $1 million. The Supreme Court has now overturned that judgment. (Monsanto, which was acquired by Bayer in 2018, continues to market and defend Roundup under the Monsanto name in many legal proceedings.)
The ruling has significant implications for Roundup litigation in the United States, but it also raises broader questions about the role of regulators, scientific evidence, and public accountability that extend well beyond America.
What the Us Supreme Court Actually Decided
The ruling turns on a single legal concept: federal preemption. US federal law (the Federal Insecticide, Fungicide, and Rodenticide Act, or FIFRA) gives the Environmental Protection Agency (EPA) sole authority to decide what goes on a pesticide label. The Court ruled that because the EPA has repeatedly reviewed glyphosate and decided it does not require a cancer warning, no US state can effectively force a company to add one through the courts.
In plain terms: as long as Bayer/Monsanto does what the EPA tells it to do, it cannot be held liable in state courts for not warning consumers about cancer risks — even if a jury concludes it should have.
The decision was not unanimous. Justices Jackson and Gorsuch dissented strongly, arguing that the law actually requires manufacturers to keep labels up to date with any necessary warnings, regardless of what the EPA has previously approved. Justice Jackson wrote that the ruling “unjustifiably closes the courthouse doors” to people like John Durnell.
Why EPA and IARC Reached Different Conclusions
The EPA has maintained since 1991 that glyphosate is “not likely to cause cancer in humans.” Regulatory agencies in Canada, Australia, Japan, and the EU have reached similar conclusions.
However, the International Agency for Research on Cancer (IARC) — a body of the World Health Organisation — classified glyphosate as a “probable carcinogen” in 2015. This is the classification that prompted thousands of lawsuits in the US, and it sits at the heart of the scientific controversy that this ruling has now, in effect, placed beyond the reach of American courts.
Regulatory agencies weigh economic costs and benefits alongside health risks. Independent scientific bodies like IARC focus purely on the evidence for carcinogenicity. They are not always asking the same question, which is why they sometimes reach different answers.
What the Monsanto Ruling Means for New Zealand
This ruling applies only in the United States. It does not directly change New Zealand law or the regulatory position of the Environmental Protection Authority (EPA NZ), which makes its own assessments of glyphosate.
However, the decision matters here for several reasons:
1. It removes a major accountability mechanism. For years, US jury verdicts have been one mechanism through which companies could be held accountable over product warnings. This ruling substantially narrows that pathway, placing even greater importance on regulatory oversight and the decisions made by agencies such as the EPA.
2. Glyphosate remains one of the most widely used herbicides in New Zealand. It is widely used by local councils on roadsides and in parks, by farmers, and in home gardens. It appears as residues in some New Zealand food products. The question of what risk level is “acceptable” is one our regulators must answer — and they should be doing so transparently, with independent scientific scrutiny.
3. New Zealand’s own review process deserves renewed scrutiny. EPA New Zealand has not undertaken a comprehensive reassessment of glyphosate in recent years. As scientific evidence continues to evolve, New Zealanders are entitled to ask whether the current regulatory approach is keeping pace and whether a more continuous review process—similar to the one recently introduced in Canada—would provide greater public confidence.
Should Regulators Have the Final Say?
One of the broader questions raised by the decision is how much weight should be placed on regulatory approval. The majority held that EPA-approved labels cannot be overridden through state failure-to-warn lawsuits. The dissent argued that this risks closing the courts to people who believe important warnings have been omitted, particularly if scientific understanding evolves after a product has been approved.
What you can do
- Stay informed. Court decisions like this don’t end the scientific discussion. Continue following new research, regulatory developments, and independent analysis as our understanding of glyphosate evolves.
- Find out what’s happening in your own community. Ask your local council whether glyphosate is used in parks, playgrounds, berms, sports fields, and other public spaces. If they do use it, ask what alternatives have been considered and how those decisions are reviewed. Our Council Herbicide Transparency Project is helping build a nationwide picture of council herbicide use across New Zealand.
- Support independent testing and research. Independent laboratory testing and community-funded investigations provide an additional source of information alongside regulatory assessments. They help ensure important questions continue to be asked and answered.
- Help keep the conversation going. If you value independent reporting on glyphosate in New Zealand, consider sharing our articles, following No More Glyphosate NZ, or supporting our work. Every share, donation, and conversation helps expand public understanding and supports future research and testing.
Whether people agree with the Court’s reasoning or not, the decision reinforces one reality: when regulators become the final authority over product warnings, public confidence in those regulators becomes more important than ever.
That raises an important question for New Zealand. If our regulators are the primary safeguard between scientific uncertainty and public exposure, how often should their conclusions be revisited as new evidence emerges?
No More Glyphosate NZ (NMGNZ) advocates for transparency about glyphosate use in our food, playgrounds, and environment.
Further Reading
This Supreme Court ruling may have been decided under US law, but the broader questions it raises about regulation, scientific evidence, transparency, and public accountability extend well beyond the United States.
US Supreme Court Decision: Monsanto Co. v. Durnell [PDF]
Read the Supreme Court’s decision in the case that reshaped failure-to-warn lawsuits involving Roundup. The judgment explains why the Court concluded that federal pesticide law pre-empts state-law warning claims when the EPA has not required a cancer warning.
International Agency for Research on Cancer (IARC): Glyphosate Assessment
The IARC Monograph explains why glyphosate was classified as a “probably carcinogenic to humans” (Group 2A) in 2015. It remains one of the central scientific references in the global debate.
EPA New Zealand – Chemical Reassessment Programme
How does EPA New Zealand decide whether to reassess an approved chemical? This page outlines the reassessment process and the factors considered when new information becomes available.
Health Canada: Continuous Oversight of Pesticides
Canada recently placed glyphosate within its Continuous Oversight framework, recognising the volume of new information emerging since the herbicide’s last major review. It represents a different approach to ongoing regulatory monitoring.
If Canada Can Continuously Monitor Glyphosate, Why Can’t New Zealand?
Our analysis of Canada’s new Continuous Oversight programme and what it could mean for New Zealand’s approach to reviewing glyphosate.
Safe According to Whom? What Regulators Mean When They Say a Chemical Is Safe
What do regulators actually mean when they describe a chemical as “safe”? This article explores how regulatory risk assessments differ from hazard classifications and why that distinction often causes confusion.
Monsanto v. Durnell: Bayer’s Bid to End Roundup Lawsuits
Published before the Supreme Court ruling, this article explains the background to the case, why it reached the Court, and what was at stake for thousands of Roundup lawsuits.
The Missing Piece in the Glyphosate Debate: Your Gut Microbiome
Research into the human microbiome is opening new avenues for understanding how chemicals may affect health beyond traditional toxicology. This article explores why some researchers believe the gut microbiome deserves greater attention in glyphosate risk assessments.
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