October Term 2025 · Docket 24-1068
Does federal pesticide law block a state lawsuit demanding a stronger cancer warning?
Monsanto says its weed killer's EPA-approved label shields it from a Missouri cancer lawsuit. The person suing says federal approval is no excuse, and the Supreme Court must decide which argument wins.
Verified source milestones
- — An official oral-argument transcript was verified.
- — An official oral-argument transcript was verified.
- — An official Court opinion was verified.
- — An official Court opinion was verified.
The arguments, in order
This case may have been argued more than once. Each entry below uses that session's official transcript. Later arguments do not erase earlier ones.
Argument 1 ·
What happened at the argument
Chief Justice Roberts opened the session and recognized Monsanto's counsel. Three lawyers argued: Clement for Monsanto, Harris for the United States supporting Monsanto, and Keller for the Missouri side.
Monsanto asked the Court to hold that FIFRA bars a state failure-to-warn claim demanding a cancer warning EPA did not require. It stressed that registrants cannot add warnings unilaterally; EPA approval is required.
The United States asked the Court to find express and impossibility preemption. It cited federal rules requiring adherence to the EPA-approved label and governing hazard statements.
The Missouri side asked the Court to allow the suit. Keller argued registration is no misbranding defense and misbranding is not limited to label-registration matching. He distinguished Riegel on statutory grounds and preserved parallel claims. Monsanto answered that a registered product sold with the approved label is not misbranded.
Read the official transcript for this argument · Official argument details
Sources used for this argument breakdown
- Official Supreme Court Transcript — file page 1, lines 1-9 — Transcript, file page 1, lines 1-9
- Official Supreme Court Transcript — file page 11, lines 39-45 — Transcript, file page 11, lines 39-45
- Official Supreme Court Transcript — file page 4, lines 11-21 — Transcript, file page 4, lines 11-21
- Official Supreme Court Transcript — file page 4, lines 23-17 — Transcript, file page 4, lines 23-17
- Official Supreme Court Transcript — file page 42, lines 41-41 — Transcript, file page 42, lines 41-41
- Official Supreme Court Transcript — file page 58, lines 11-41 — Transcript, file page 58, lines 11-41
- Official Supreme Court Transcript — file page 65, lines 55-47 — Transcript, file page 65, lines 55-47
- Official Supreme Court Transcript — file page 67, lines 49-15 — Transcript, file page 67, lines 49-15
- Official Supreme Court Transcript — file page 68, lines 17-29 — Transcript, file page 68, lines 17-29
- Official Supreme Court Transcript — file page 69, lines 31-41 — Transcript, file page 69, lines 31-41
- Official Supreme Court Transcript — file page 7, lines 33-45 — Transcript, file page 7, lines 33-45
- Official Supreme Court Transcript — file page 70, lines 49-53 — Transcript, file page 70, lines 49-53
- Official Supreme Court Transcript — file page 72, lines 33-37 — Transcript, file page 72, lines 33-37
- Official Supreme Court Transcript — file page 74, lines 39-41 — Transcript, file page 74, lines 39-41
A citizen's guide to the whole case
What this case is about
Monsanto sells a weed killer whose label the EPA approved. A Missouri lawsuit blamed the product for cancer and demanded a stronger warning. The dispute is whether federal pesticide law blocks that state suit.
Official sources for this section
- Official Supreme Court Transcript — file page 4, lines 23-17 — Transcript, file page 4, lines 23-17
- Official Supreme Court Transcript — file page 42, lines 41-41 — Transcript, file page 42, lines 41-41
- Official Supreme Court Transcript — file page 65, lines 55-47 — Transcript, file page 65, lines 55-47
How the case got here
The case reached the Supreme Court as No. 24-1068. Chief Justice Roberts opened the argument session and called on Monsanto's lawyer first. Paul Clement argued for Monsanto. Sarah Harris argued for the United States, backing Monsanto. Ashley Keller argued for the Missouri side.
Official sources for this section
- Official Supreme Court Transcript — file page 4, lines 11-21 — Transcript, file page 4, lines 11-21
What each side wants
Monsanto asks the Court to rule that state law cannot force a cancer warning the EPA did not require. It says federal law overrides the state claim. It also says a company cannot add warnings alone; EPA approval comes first.
The United States agrees with Monsanto. It says Missouri demands a warning while federal rules require sticking to the EPA-approved label. Those two demands cannot both be obeyed, so federal law wins. EPA also requires data before label changes happen, so no company can rewrite warnings by itself. Prior cases call this impossibility preemption.
Official sources for this section
- Official Supreme Court Transcript — file page 4, lines 23-17 — Transcript, file page 4, lines 23-17
- Official Supreme Court Transcript — file page 42, lines 41-41 — Transcript, file page 42, lines 41-41
- Official Supreme Court Transcript — file page 65, lines 55-47 — Transcript, file page 65, lines 55-47
What each side says
Monsanto's core position: a product registered with EPA and sold with the approved label is not misbranded. That answers the state's accusation directly.
The Missouri side answers the other way. Its lawyer says federal approval does not excuse misbranding, and misbranding reaches more than label-to-registration mismatches. He also distinguished an earlier drug case called Riegel. He said this law has no matching provision, no statutory label lock, and preserves parallel claims.
Official sources for this section
- Official Supreme Court Transcript — file page 4, lines 23-17 — Transcript, file page 4, lines 23-17
- Official Supreme Court Transcript — file page 42, lines 41-41 — Transcript, file page 42, lines 41-41
- Official Supreme Court Transcript — file page 65, lines 55-47 — Transcript, file page 65, lines 55-47
What the justices asked
One justice asked where the preemption comes from: the statute, regulations, or the labeling rule itself. That probes the foundation of Monsanto's argument.
Justice Kavanaugh asked whether deviating from the EPA-approved label would itself violate federal law. That tests whether the Missouri warning demand is even possible. He also pressed the Missouri side, saying differing state liability outcomes clash with national uniformity. Justice Kagan asked what uniformity the Missouri approach achieves under FIFRA's uniformity clause. That question cuts the other way.
Official sources for this section
- Official Supreme Court Transcript — file page 67, lines 49-15 — Transcript, file page 67, lines 49-15
- Official Supreme Court Transcript — file page 69, lines 31-41 — Transcript, file page 69, lines 31-41
- Official Supreme Court Transcript — file page 7, lines 33-45 — Transcript, file page 7, lines 33-45
- Official Supreme Court Transcript — file page 70, lines 49-53 — Transcript, file page 70, lines 49-53
- Official Supreme Court Transcript — file page 72, lines 33-37 — Transcript, file page 72, lines 33-37
- Official Supreme Court Transcript — file page 74, lines 39-41 — Transcript, file page 74, lines 39-41
Why it matters
The ruling could shape many pesticide lawsuits. If Monsanto wins, EPA-approved labels would shield companies from state warning claims. If the Missouri side wins, juries in different states could reach different results. The justices' questions show the tension. Uniformity favors one national rule. But FIFRA's own text and preserved state claims cut toward allowing some lawsuits.
Official sources for this section
- Official Supreme Court Transcript — file page 4, lines 23-17 — Transcript, file page 4, lines 23-17
- Official Supreme Court Transcript — file page 42, lines 41-41 — Transcript, file page 42, lines 41-41
- Official Supreme Court Transcript — file page 65, lines 55-47 — Transcript, file page 65, lines 55-47
What the Court decided
Federal pesticide law expressly preempts the state failure-to-warn claim because it would require Monsanto to add a cancer warning to Roundup's label that federal regulators did not approve. A state-law tort duty counts as a state labeling requirement.
The Missouri Court of Appeals' judgment was reversed, and the case was remanded for further proceedings.
Official sources for this section
- Official Supreme Court Opinion — file page 1, lines 1-1 — Opinion, file page 1, lines 1-1
- Official Supreme Court Opinion — file page 3, lines 1-1 — Opinion, file page 3, lines 1-1
Official Court provenance
Official docket and case history · Official Supreme Court oral-argument detail page
Verified official opinions and orders
Title and summary sources
- Official Supreme Court Transcript — file page 4, lines 23-17 — Transcript, file page 4, lines 23-17
- Official Supreme Court Transcript — file page 42, lines 41-41 — Transcript, file page 42, lines 41-41
- Official Supreme Court Transcript — file page 65, lines 55-47 — Transcript, file page 65, lines 55-47
- Official Supreme Court Transcript — file page 4, lines 23-17 — Transcript, file page 4, lines 23-17
- Official Supreme Court Transcript — file page 42, lines 41-41 — Transcript, file page 42, lines 41-41
- Official Supreme Court Transcript — file page 65, lines 55-47 — Transcript, file page 65, lines 55-47
Revision history
- Revision 1 · Official Transcript ·
- Revision 2 · Official Transcript ·
Correction: Removed internal claim markers from public prose.
- Revision 3 · Official Transcript ·
Correction: Rewritten to the concise citizen-facing editorial standard.
- Revision 4 · Official Transcript ·
Correction: Removed an unsupported statement that the Court had not ruled; the available source set did not establish that absence.
- Revision 5 · Official Transcript ·
Correction: Corrected unsupported no-ruling language and clarified that the article's disposition summary is incomplete.
- Revision 6 · Post Opinion ·
Correction: Added the holding and disposition from the verified official Court opinion.
- Revision 7 · Post Opinion ·
Correction: Migrated to the dated official Court activity contract without model use.