Amicus Curiae Brief — Monsanto Company, Petitioner v. John L. Durnell
Supreme Court briefMar 31, 2026
Ask Donna
What actually matters in this document.
Text
No. 24-1068
IN THE
Supreme Court of the United States
__________
MONSANTO COMPANY,
Petitioner,
v.
JOHN L. DURNELL,
Respondent.
__________
On Writ of Certiorari
to the Missouri Court of Appeals
__________
BRIEF OF ROUNDUP AND PARAQUAT
MDL LEADERSHIP AS AMICI CURIAE
IN SUPPORT OF RESPONDENT
__________
ROBIN L. GREENWALD
WEITZ & LUXENBERG P.C.
700 Broadway
New York, NY 10003
(212) 558-5500
KHALDOUN A. BAGHDADI
WALKUP, MELODIA, KELLY
& SCHOENBERGER
650 California Street
26th Floor
San Francisco, CA 94108
(415) 212-4350
March 31, 2026
DAVID C. FREDERICK
Counsel of Record
DEREK C. REINBOLD
KYLE B. GRIGEL
ALYSSA J. PICARD
KELLOGG, HANSEN, TODD,
FIGEL & FREDERICK,
P.L.L.C.
1615 M Street, N.W.
Suite 400
Washington, D.C. 20036
(202) 326-7900
(dfrederick@kellogghansen.com)
QUESTION PRESENTED
The Question Presented, as modified by the Court,
is:
Whether the Federal Insecticide, Fungicide, and
Rodenticide Act preempts a label-based failure-towarn claim where EPA has not required the warning.
ii
TABLE OF CONTENTS
Page
QUESTION PRESENTED .......................................... i
TABLE OF AUTHORITIES ...................................... iii
GLOSSARY ..................................................................x
INTEREST OF AMICI CURIAE ................................ 1
SUMMARY OF ARGUMENT .................................... 2
STATEMENT .............................................................. 5
A. Statutory And Regulatory Background .......... 5
B. Factual Background ......................................... 8
ARGUMENT ............................................................. 15
I. FIFRA DOES NOT EXPRESSLY
PREEMPT LABEL-BASED FAILURETO-WARN CLAIMS ....................................... 15
A. Failure-To-Warn Claims Like Respondent’s Are Consistent With FIFRA,
Which Reserves Significant Authority
To States .................................................... 15
B. Monsanto’s Express-Preemption Arguments Lack Merit ...................................... 20
II. FIFRA DOES NOT IMPLICITLY
PREEMPT LABEL-BASED FAILURETO-WARN CLAIMS ....................................... 27
III. MONSANTO’S POSITION WOULD
HAVE SUBSTANTIAL NEGATIVE
EFFECTS ....................................................... 31
CONCLUSION.......................................................... 32
iii
TABLE OF AUTHORITIES
CASES
Page
Bates v. Dow AgroSciences LLC, 544 U.S. 431
(2005) ................................................ 1-8, 15-20, 22,
24-26, 28-29, 31-32
Carson v. Monsanto Co.:
72 F.4th 1261 (11th Cir. 2023) ............................ 15
92 F.4th 980 (11th Cir. 2024) .........................19, 31
Cipollone v. Liggett Grp., Inc., 505 U.S. 504
(1992) ..................................................................... 6
Ferebee v. Chevron Chem. Co., 736 F.2d 1529
(D.C. Cir. 1984) ...................................................... 7
Hardeman v. Monsanto Co., 997 F.3d 941
(9th Cir. 2021).......................... 19, 22, 24-25, 29-31
Kiakombua v. Wolf, 498 F. Supp. 3d 1 (D.D.C.
2020)..................................................................... 21
League of United Latin Am. Citizens v. Regan,
996 F.3d 673 (9th Cir. 2021) ............................... 23
Medtronic, Inc. v. Lohr, 518 U.S. 470 (1996) .......... 15,
20, 24-25
Merck Sharp & Dohme Corp. v. Albrecht,
587 U.S. 299 (2019) ........................................27, 30
Moore v. Ford Motor Co., 332 S.W.3d 749
(Mo. 2011) ............................................................ 20
NRDC v. EPA, 38 F.4th 34 (9th Cir. 2022) .....3, 12, 20
PLIVA, Inc. v. Mensing, 564 U.S. 604 (2011) ......3, 25,
28-29
iv
Red River Valley Sugarbeet Growers Ass’n v.
Regan, 85 F.4th 881 (8th Cir. 2023) ................... 23
Riegel v. Medtronic, Inc., 552 U.S. 312 (2008)... 2, 24-25
Sprietsma v. Mercury Marine, 537 U.S. 51
(2002) ................................................................... 31
United States v. ICC, 337 U.S. 426 (1949) ............... 21
Wisconsin Pub. Intervenor v. Mortier, 501 U.S.
597 (1991) .............................................................. 7
WorldCom, Inc. v. FCC, 246 F.3d 690 (D.C. Cir.
2001)..................................................................... 21
Wyeth v. Levine, 555 U.S. 555 (2009) ........ 4, 27-28, 30
STATUTES AND REGULATIONS
Federal Environmental Pesticide Control Act of
1972, Pub. L. No. 92-516, § 2, 86 Stat. 973,
984 .......................................................................... 5
Federal Food, Drug, and Cosmetic Act,
21 U.S.C. § 301 et seq. ...................................28, 30
21 U.S.C. § 360k(a)(2).......................................... 24
Federal Insecticide, Fungicide, and Rodenticide
Act, 7 U.S.C. §§ 136-136y ....................... 1-7, 15-22,
24-29, 31-32
§ 136(q) ................................................................... 7
§ 136(q)(1)(A) ......................................................... 6
§ 136(q)(1)(F).................................................... 6, 24
§ 136(q)(1)(G) .............................. 2, 6, 19-20, 22, 24
§ 136a(a) ................................................................. 5
§ 136a(c) ................................................................. 5
v
§ 136a(c)(1)(C) .................................................. 6, 29
§ 136a(c)(2) ........................................................... 22
§ 136a(c)(5) ............................................................. 5
§ 136a(c)(5)(B)-(D) ........................................... 6, 22
§ 136a(f )(1) ........................................................... 29
§ 136a(f )(2) .............................................. 3, 7, 21-24
§ 136d(a)(2) ............................................................ 6
§ 136d(b) ................................................................. 7
§ 136j ...................................................................... 7
§ 136j(a)(1)(E) ..................................................... 6-7
§ 136j(a)(2)(C) ........................................................ 6
§ 136j(a)(2)(M)........................................................ 6
§ 136k ..................................................................... 7
§ 136l ...................................................................... 7
§ 136v ..................................................................... 7
§ 136v(a) ................................. 2, 8, 15, 17-19, 24-25
§ 136v(b) ............................................ 2, 8, 16-19, 24
§ 136v(c) ............................................................... 15
§ 136v(c)(1) ........................................................... 15
§ 136w-1 ................................................2, 15, 17, 25
Medical Device Amendments of 1976, Pub. L.
No. 94-295, 90 Stat. 539 .................................. 2, 24
15 U.S.C. § 1333 .......................................................... 6
15 U.S.C. § 4402(a)(1) ................................................. 6
Cal. Food & Agric. Code §§ 14001-14015 ................. 13
21 C.F.R. § 801.430(c) ................................................. 6
vi
40 C.F.R.:
Pt. 152:
§ 152.46(a) ...................................................... 29
§ 152.50(e)....................................................... 29
Pt. 156:
§ 156.64 ........................................................... 26
Pt. 158:
§ 158.500(d) ...................................................... 5
Pt. 159 .................................................................... 6
Cal. Code Regs. tit. 3:
§ 6420(a) ............................................................... 13
§ 6466 ................................................................... 13
§ 6470 ................................................................... 13
ADMINISTRATIVE MATERIALS
Shelley DuTeaux et al., Cal. Dep’t of Pesticide
Regulation, Preliminary Report of the Potential Human Health Outcomes Resulting
from Paraquat Exposure (Dec. 2024),
https://www.cdpr.ca.gov/wp-content/uploads/
2024/12/paraquat_preliminary_human_
health_report.pdf ............................................ 12-13
Env’t Prot. Agency:
EPA Withdraws Glyphosate Interim Decision
(Sept. 23, 2022), https://perma.cc/EU77LMGN .................................................................. 21
vii
Final Rule, Optional Procedures for Classification of Pesticide Uses by Regulation, 43
Fed. Reg. 5782 (Feb. 9, 1978) ................................ 9
Off. of Pesticide Programs, Pesticide Registration Notice 98-10 (Oct. 22, 1998), https://
perma.cc/5JC7-ESFR .......................................... 29
Off. of Pesticide Programs, Revised Glyphosate Issue Paper: Evaluation of Carcinogenic Potential (Dec. 12, 2017), https://
perma.cc/2WJM-MT7R ................................... 11-12
Paraquat Dichloride: Interim Registration
Review Decision (July 2021), https://perma.
cc/4B7K-5G5E ...................................................... 13
Paraquat Dichloride: Systematic Review
(June 26, 2019), https://perma.cc/N75Z8VZ7 ..................................................................... 12
Reregistration Eligibility Decision (RED)
Glyphosate (Sept. 1993), https://perma.cc/
528H-F4FN .......................................................... 30
Reregistration Eligibility Decision (RED)
Paraquat Dichloride (Aug. 1997), https://
perma.cc/Z7DP-KLHA ......................................... 12
Fed. Jud. Ctr., Reference Manual on Scientific
Evidence (3d ed. 2011), https://perma.cc/V9UT98DR .................................................................... 13
OTHER MATERIALS
Am. Parkinson Disease Ass’n, Paraquat is
banned in 70+ countries, but still legal in the
US (Feb. 24, 2026) ............................................... 13
viii
Bayer, Missouri court grants preliminary
approval of Roundup™ class settlement to
resolve current and future claims (Mar. 4,
2026)..................................................................... 14
Brief Amicus Curiae for the United States in
Support of Plaintiffs-Appellants, Etcheverry
v. Tri-Ag Serv., Inc., 993 P.2d 366 (Cal. 2000)
(No. S072524, filed Mar. 1999) ............................ 19
Brief for the United States as Amicus Curiae,
Monsanto Co. v. Hardeman, No. 21-241
(U.S. May 10, 2022) .................................. 23-24, 32
Class Action Settlement Agreement, In re
Roundup Prods. Liab. Litig., No. 3:16-md2741-VC, ECF #12509-2 (N.D. Cal. Feb. 3,
2021)..................................................................... 26
Class Action Settlement Agreement, King v.
Monsanto Co., No. 2622-CC00325 (Mo. Cir.
Ct. Feb. 17, 2026)................................................. 14
Nathan Donley, The USA lags behind other
agricultural nations in banning harmful
pesticides, 18 Envtl. Health #44 (2019) .............. 23
Sharon Lerner, The Paraquat Poisoning Problem (Mar. 24, 2021), https://theintercept.
com/2021/03/24/paraquat-poisoningsyngenta/ ................................................................ 9
PAN Germany, Paraquat and Suicide (2003),
https://www.pan-germany.org/download/
fact_paraquat2.pdf ................................................ 9
Restatement (Third) of Torts: Products Liability
(1998) ................................................................... 25
ix
Caroline M. Tanner et al., Rotenone, Paraquat,
and Parkinson’s Disease, 119 Envtl. Health
Persp. 866 (June 2011) ........................................ 11
Martin van den Berg, Retraction Notice to
“Safety Evaluation and Risk Assessment of
the Herbicide Roundup and Its Active Ingredient, Glyphosate, for Humans” [31 Regul.
Toxicol. & Pharm. 117-65 (2000)], published
online December 2025, https://bit.ly/4aefz1P ...... 10
x
GLOSSARY
BIO.App.
Appendix to Brief in Opposition
for Respondent, Monsanto Co. v.
Durnell, No. 24-1068 (U.S. June 9,
2025)
Botham.Dep.
Deposition Transcript of Dr. Philip
Botham, Hoffmann v. Syngenta
Crop Prot., LLC, No. 17-L-517 (Ill.
Cir. Ct., 20th Jud. Cir., St. Clair
Cnty. Feb. 25-26 & June 17-19,
2020), available at https://www.
thenewlede.org/wp-content/uploads/2022/11/Dr.-Bothamdeposition-transcript-2020.pdf
Dixon.Dep.
Deposition Transcript of Syngenta,
by and through its Representative
Montague Dixon, Hoffmann v.
Syngenta Crop Prot., LLC, No. 17L-517 (Ill. Cir. Ct., 20th Jud. Cir.,
St. Clair Cnty. June 24, 2020),
available at https://www.thenewlede.org/wp-content/uploads/2023/
05/Monty-Dixon-deposition-2020.
EPA
Environmental Protection Agency
FDCA
Federal Food, Drug, and Cosmetic
Act, 21 U.S.C. § 301 et seq.
FIFRA
Federal Insecticide, Fungicide, and
Rodenticide Act, 7 U.S.C. §§ 136136y
IARC
International Agency for Research
on Cancer
xi
MDAs
Medical Device Amendments of
1976, Pub. L. No. 94-295, 90 Stat.
539
MDL
Multidistrict Litigation
Ouzts.Dep.
Deposition Transcript of Syngenta,
by and through its Representative
Clark Ouzts, Hoffmann v. Syngenta
Crop Prot., LLC, No. 17-L-517 (Ill.
Cir. Ct., 20th Jud. Cir., St. Clair
Cnty. June 22 & Sept. 28, 2020),
available at https://www.thenewlede.org/wp-content/uploads/2023/
05/Clark-Ouzts-deposition-2020.
Patterson.Dep.
Deposition Transcript of Timothy
Patterson, Hoffmann v. Syngenta
Crop Prot., LLC, No. 17-L-517 (Ill.
Cir. Ct., 20th Jud. Cir., St. Clair
Cnty. Jan. 22, 2021), available at
https://www.thenewlede.org/wpcontent/uploads/2023/05/Pattersondeposition-2021.pdf
Pet.App.
Appendix to Petition for Writ
of Certiorari, Monsanto Co. v.
Durnell, No. 24-1068 (U.S. Apr. 4,
2025)
POEA
polyethoxylated tallow amine
PPE
personal protective equipment
RA
Respondent’s Appendix, Durnell v.
Monsanto Co., ED112410 (Mo. Ct.
App. Nov. 7, 2024)
xii
Tr.
Transcript on Appeal in No.
ED112410 (Mo. Ct. App. June 13,
2024)
U.S. Hardeman
Br.
Brief for the United States as Amicus Curiae, Monsanto Co. v. Hardeman, No. 21-241 (U.S. May 10,
2022)
INTEREST OF AMICI CURIAE 1
Amici are the court-appointed leaders of MDLs
involving plaintiffs harmed by the pesticides Roundup
and paraquat. See In re Roundup Prods. Liab. Litig.,
MDL No. 2741 (N.D. Cal.); In re Paraquat Prods. Liab.
Litig., MDL No. 3004 (S.D. Ill.). Amici represent more
than 5,000 individuals who allege that glyphosatebased Roundup caused them to develop non-Hodgkin
lymphoma. And amici represent approximately 6,525
individuals who allege that they developed Parkinson’s
disease following exposure to paraquat, a restricteduse herbicide banned in many countries.
Amici have a substantial interest in this case
because Monsanto’s preemption theory—that FIFRA
bars failure-to-warn claims whenever EPA has not
required a warning—would directly affect their
clients’ cases. Accepting Monsanto’s position would
allow manufacturers to invoke EPA’s silence as a
defense, even when the manufacturer failed to disclose
material safety information to the agency. That concern is concrete here: Amici’s cases include evidence
that Monsanto and Syngenta suppressed studies and
withheld data from EPA, contributing to the absence
of warnings on the labels they invoke as preemptive.
Amici offer a practical perspective. They have
extensive experience with FIFRA’s registration process,
manufacturers’ interactions with EPA, and the role of
preemption defenses in mass tort litigation. That
experience informs amici’s view that FIFRA preserves
the “concurrent authority of the Federal and State
Governments” and that state-law remedies “aid,
rather than hinder, the functioning of FIFRA.” Bates
v. Dow AgroSciences LLC, 544 U.S. 431, 450-51 (2005).
1 No counsel for a party authored this brief in whole or part.
No person or entity other than amici or counsel made a monetary
contribution to the preparation or submission of this brief.
2
SUMMARY OF ARGUMENT
The Court granted certiorari to decide whether the
Federal Insecticide, Fungicide, and Rodenticide Act
preempts a label-based failure-to-warn claim where
EPA has not required the warning. The answer is no.
I. FIFRA preserves a broad role for state regulation of pesticides—including the power to ban a federally registered pesticide. Against that backdrop, Monsanto’s claim that FIFRA strips States of the lesser
authority to require reasonable warnings lacks merit.
A. FIFRA “authorizes a relatively decentralized
scheme that preserves a broad role for state regulation.” Bates, 544 U.S. at 450. States may ban or
restrict the use of any EPA-approved pesticide. 7 U.S.C.
§ 136v(a).2 And they bear “primary enforcement
responsibility” for pesticide use violations. § 136w-1.
The one limit on that authority is a “narrow” preemption provision, Bates, 544 U.S. at 452, which bars only
state labeling requirements that are “in addition to or
different from” FIFRA’s own requirements, § 136v(b).
Because FIFRA does not give EPA final say over
pesticide use, a state-law failure-to-warn claim based
on inadequate instructions for a pesticide’s safe use
does not add to or differ from any preemptive federal
requirement. Nor does a state-law claim that parallels FIFRA’s misbranding provisions, which require
warnings “adequate to protect health,” § 136(q)(1)(G).
B. A fair accounting of FIFRA’s registration
scheme rebuts Monsanto’s and the United States’
arguments. Unlike the Medical Device Amendments
at issue in Riegel v. Medtronic, Inc., 552 U.S. 312
(2008), FIFRA does not treat registration as a comprehensive federal safety determination that displaces
2 Except where noted, U.S. Code citations are to Title 7.
3
state authority. Registration is only “prima facie
evidence” that a pesticide complies with the statute.
§ 136a(f )(2). It is not “a defense for the commission of
any offense” under FIFRA, including misbranding.
Id. The manufacturer—not EPA—drafts the label,
submits the supporting data, and bears a continuing
obligation to ensure the label is not misleading. See
Bates, 544 U.S. at 438. That allocation of responsibility is the opposite of when agency approval immunizes
a manufacturer from liability.
The need for state-law remedies is acute here
because EPA has not meaningfully evaluated the
risks underlying these cases. The agency never has
assessed whether Roundup as formulated—including
its surfactant and several carcinogenic contaminants—
causes cancer. Nor has the agency properly assessed
the cancer-causing potential of Roundup’s active
ingredient: When EPA determined that glyphosate
alone is “not likely to be carcinogenic,” the Ninth
Circuit vacated that conclusion as “the hallmark of
arbitrary action.” NRDC v. EPA, 38 F.4th 34, 49, 51
(9th Cir. 2022). Similarly, EPA has failed to evaluate
paraquat’s capacity to cause Parkinson’s disease.
Despite decades of emerging evidence, the agency
never has required neurotoxicity testing—but has
cited the absence of such testing as proof of safety.
Where EPA is silent on warnings imposed under state
law, preemption is inappropriate.
II. Monsanto’s implied-preemption arguments likewise do not withstand scrutiny. Unlike the genericdrug manufacturers in PLIVA, Inc. v. Mensing, 564
U.S. 604 (2011), pesticide registrants bear primary
responsibility for their own labels and can act independently to amend them. And there is no “clear evidence” that EPA would have rejected any adequate
4
warning. Wyeth v. Levine, 555 U.S. 555, 571 (2009).
Monsanto never proposed one—not a cancer warning,
an instruction that consumers wear personal protective equipment like masks or gloves, or even an
acknowledgment that authoritative scientific bodies
have concluded glyphosate is carcinogenic.
III. State-law tort actions serve FIFRA’s purposes
by exposing undisclosed dangers and giving manufacturers “added dynamic incentives to continue to keep
abreast of all possible injuries stemming from use of
their product.” Bates, 544 U.S. at 451. That function
is critical here, where the statutory scheme depends
heavily on manufacturer disclosure. The record shows
that manufacturers withheld safety data from EPA
for years—a fact that surfaced only through private
litigation, not agency oversight. Accepting Monsanto’s
preemption theory would invert that framework:
rewarding nondisclosure, converting manufacturercreated regulatory gaps into immunity, and leaving
injured individuals with no remedy for harms that
adequate warnings could have prevented.
5
STATEMENT
A. Statutory And Regulatory Background
1. In 1947, Congress enacted FIFRA to protect
against adulterated and ineffective pesticides. FIFRA
initially had no health or environmental protections.
Congress amended the statute in 1972, in the wake of
Rachel Carson’s Silent Spring and the controversy
over DDT, to require EPA to consider risks to health
and the environment when deciding whether to register a pesticide. See Federal Environmental Pesticide
Control Act of 1972, Pub. L. No. 92-516, § 2, 86 Stat.
973, 984. FIFRA today governs “the use, as well
as the sale and labeling, of pesticides.” Bates 544 U.S.
at 437. Congress has not amended FIFRA in any
material respect since this Court’s 2005 Bates decision.
FIFRA requires manufacturers to “register” their
pesticides with EPA. § 136a(a) (“Requirement of registration”). EPA registration confers a limited license
to market a pesticide. FIFRA provides that EPA
“shall” register a pesticide if it determines that the
label complies with the statute’s requirements, the
manufacturer’s claims about the product’s composition are warranted, the pesticide will perform its
intended function, and its use “will not generally
cause unreasonable adverse effects” on human health
or the environment. § 136a(c)(5).
The manufacturer bears the burden of making that
showing, although it is not a demanding one. The
manufacturer must submit data demonstrating that
the proposed pesticide satisfies FIFRA’s standards.
§ 136a(a), (c). As to carcinogenicity, EPA’s regulations
require only two rodent studies. See 40 C.F.R.
§ 158.500(d) (Table, Guideline No. 870.4200).
Based on those submissions, EPA then determines
whether the product meets FIFRA’s standards,
6
including whether it will avoid unreasonable harm
to human health and the environment and whether
its label is not “misbranded.” § 136a(c)(5)(B)-(D). A
pesticide is “misbranded” if its label contains a statement that is “false or misleading in any particular,”
§ 136(q)(1)(A), or omits adequate instructions for
use, necessary warnings, or cautionary statements,
§ 136(q)(1)(F), (G).
2. FIFRA leaves the drafting of the label to the
registrant. § 136a(c)(1)(C). This feature distinguishes
FIFRA from other laws, including “the cigarette labeling law at issue in Cipollone [v. Liggett Group, Inc.,
505 U.S. 504 (1992)], which prescribed certain immutable warning statements.” Bates, 544 U.S. at 451; see
also 15 U.S.C. §§ 1333, 4402(a)(1). EPA’s regulations
also do not dictate the language to be used for the bulk
of each label. Cf. 21 C.F.R. § 801.430(c) (specific toxicshock warnings).
Because EPA relies on manufacturer-submitted
data and labeling language, and does not conduct its
own tests on a pesticide’s health and environmental
effects, FIFRA imposes requirements on registrants:
First, a registrant may not knowingly falsify any
part of a registration application, and it may not make
false or misleading statements in its labeling.
§§ 136(q)(1)(A), 136j(a)(1)(E), 136j(a)(2)(C), (M).
Second, after registration issues, the registrant
must provide EPA with information about unreasonable adverse effects on health or the environment.
§ 136d(a)(2); 40 C.F.R. pt. 159.
Third, the registrant remains responsible for ensuring that its registration and labeling comply with
FIFRA. “Because it is unlawful under the statute to
sell a pesticide that is registered but nevertheless misbranded, manufacturers have a continuing obligation
7
to adhere to FIFRA’s labeling requirements.” Bates,
544 U.S. at 438; see §§ 136(q), 136j(a)(1)(E).
3. Registration does not insulate a manufacturer
from liability. FIFRA provides that “[i]n no event
shall registration of an article be construed as a
defense” to a violation of the Act. § 136a(f )(2). Rather,
registration is only “prima facie evidence” that the
pesticide and its labeling comply with the statute. Id.
If EPA concludes that a registration no longer
complies with FIFRA, it may initiate administrative
proceedings to cancel the registration, § 136d(b),
although such proceedings are time-consuming,
expensive, and thus rare, see infra p.23. EPA also may
seize, restrict, or prohibit the sale or use of pesticides
that violate FIFRA. §§ 136j, 136k; see also § 136l
(authorizing civil and criminal penalties).
None of FIFRA’s enforcement mechanisms compensates people injured by an unsafe or mislabeled pesticide. Nor does federal law provide any other damages
remedy for those injuries. Historically, then, statelaw damages actions have provided the only means of
compensating individuals harmed by FIFRA violations. See Bates, 544 U.S. at 451; Ferebee v. Chevron
Chem. Co., 736 F.2d 1529, 1540-41 (D.C. Cir. 1984).
4. FIFRA “authorizes a relatively decentralized
scheme that preserves a broad role for state regulation.” Bates, 544 U.S. at 450; see Wisconsin Pub.
Intervenor v. Mortier, 501 U.S. 597, 613 (1991) (“[T]he
statute leaves ample room for States and localities
to supplement federal efforts even absent the express
regulatory authorization of § 136v(a).”).
Indeed,
States may ban a federally registered pesticide, even
if EPA does not consider it misbranded. Bates, 544
U.S. at 446. That authority is reflected in § 136v:
8
§ 136v. Authority of States
(a) In general
A State may regulate the sale or use of any
federally registered pesticide or device in the
State, but only if and to the extent the regulation
does not permit any sale or use prohibited by
[FIFRA].
The one statutory limit on that traditional state
authority is a “narrow” preemption provision, Bates, 544
U.S. at 452—§ 136v(b):
(b) Uniformity
Such State shall not impose or continue in effect
any requirements for labeling or packaging in
addition to or different from those required under
[FIFRA].
B. Factual Background
1. Monsanto developed the weedkiller Roundup,
whose active ingredient is glyphosate. RA4 (¶ 12);
3 Tr. 1663:23-25. The company long has marketed
Roundup as safe for consumer use without personal
protective equipment; its consumer labeling does not
require a mask, gloves, or other PPE. RA4 (¶ 13),
RA45 (¶ 38); 4 Tr. 2509:9-21, 2515:11-2516:11. Farmers, who typically buy Roundup in concentrated form,
are warned to wear gloves and to wash their clothes
after spraying it. 3 Tr. 2344:10-2347:21.
Roundup contains not only glyphosate but also a
surfactant and “[s]everal” cancer-causing contaminants, including “Ethylene oxide and 1,4-Dioxane.”
3 Tr. 2007:22-2008:2. The surfactant in the United
States is polyethoxylated tallow amine, which helps
Roundup penetrate human skin. RA44 (¶ 33); 3 Tr.
1664:3-6, 2008:12-16. POEA makes Roundup more
genotoxic and is banned in Europe. RA44 (¶ 34).
9
Monsanto never has tested whether formulated
Roundup causes cancer. BIO.App.45a. In 2009,
Monsanto’s Dr. Farmer wrote “you cannot say that
Roundup does not cause cancer. We have not done
carcinogenicity studies with ‘Roundup.’ ”
JA109
(cleaned up).
Paraquat, a commercial pesticide in use since the
1960s, poses similarly life-threatening risks. Botham.
Dep. 96-97. Acutely toxic if ingested, paraquat is a
“major suicide agent,” particularly in “developing
countries.” PAN Germany, Paraquat and Suicide 2
(2003).
Paraquat is banned in more than 70 countries, including the European Union and China. Botham.Dep.
483-85, 1210-11. It remains in use in the United
States as a “restricted-use” pesticide. 43 Fed. Reg.
5782 (Feb. 9, 1978).
Paraquat’s acute toxicity is prominently disclosed
on its label. Patterson.Dep. 26-29. But the risks from
chronic exposure are not. Patterson.Dep. 30-32. Even
compliant applicators may absorb paraquat through
skin contact or inhalation, leading to accumulation in
the brain and Parkinson’s disease. Botham.Dep. 20406, 211, 216-17, 251-52. PPE does not eliminate this
risk: a 2007 study found 10 of 15 applicators tested
positive for paraquat ingestion despite using labelrequired PPE. Ouzts.Dep. 187-97. There have been
“tens of thousands of deaths from paraquat poisoning”—“possibly more than 100,000.” Sharon Lerner,
The Paraquat Poisoning Problem (Mar. 24, 2021).
2. Both pesticides’ manufacturers knew of these
risks yet suppressed the evidence.
Monsanto registered Roundup products in the mid1970s by submitting studies from Industrial Bio-Test
Laboratories—studies that FDA later discovered were
10
fraudulent. RA4 (¶ 12), RA39 (¶ 9); RA68; 2 Tr.
1020:8-1022:24. In 1985, EPA classified glyphosate as
a possible human carcinogen. RA40 (¶ 15).
Rather than pursue additional testing to resolve
those concerns, Monsanto sought to cover them up. In
the late 1990s, after four studies concluded glyphosate
was possibly genotoxic, RA41 (¶ 22), Monsanto hired
Dr. James Parry, who concluded glyphosate could be
genotoxic and suggested further tests. BIO.App.1a8a; 3 Tr. 1702:21-1703:4. Monsanto instead replaced
Parry with Dr. Gary Williams, who published an article in 2000 concluding Roundup posed no health risk.
RA45 (¶ 39). But Monsanto wrote the article, RA46
(¶ 40), then EPA relied on it when evaluating glyphosate’s carcinogenic potential, id. (¶ 42). In December
2025, the article was retracted because Monsanto
employees’ undisclosed involvement “raise[d] serious
ethical concerns regarding the independence and
accountability of the authors of this article and the
academic integrity of the carcinogenicity studies presented.”3
Syngenta, paraquat’s primary producer, likewise
long knew paraquat increases the risk of Parkinson’s.
Botham.Dep. 324, 329, 374, 662. Yet the company assured users that paraquat “does not reach the specific
location in the brain necessary to produce Parkinson’s
symptoms.” Botham.Dep. 1072-78. Syngenta directed
employees not to measure paraquat in animal brains
because any amount “(no matter how small) will
not be perceived externally in a positive light.”
3 Martin van den Berg, Retraction Notice to “Safety Evaluation
and Risk Assessment of the Herbicide Roundup and Its Active
Ingredient, Glyphosate, for Humans” [31 Regul. Toxicol. &
Pharm. 117-65 (2000)], published online December 2025,
https://bit.ly/4aefz1P.
11
Botham.Dep. 311-15. From 2008 on, all paraquat
research required legal-department approval. Botham.
Dep. 1104-06, 1191-93.
Despite these measures, Syngenta’s own scientists
identified neurological risks. Between 2003 and 2005,
scientist Louise Marks found statistically significant
neuron loss; Syngenta withheld those findings from
EPA until December 2019, after plaintiffs’ counsel uncovered them. Botham.Dep. 315-18, 332-34, 363-64,
395-98. A 2010 study found paraquat concentrations
in exposed squirrel monkeys’ brains did not decline
over time. Syngenta chose not to disclose that study.
Botham.Dep. 813-14, 826-27. A 2011 NIH-funded
study reported a 2.5-fold increase in Parkinson’s risk
among paraquat-exposed workers. See Caroline M.
Tanner et al., Rotenone, Paraquat, and Parkinson’s
Disease, 119 Envtl. Health Persp. 866 (June 2011).
Syngenta’s privately commissioned reanalysis found
a comparable increase, but it did not disclose those
results. Botham.Dep. 395-403.
3. EPA’s regulatory response to both products has
been marked by circular reasoning and reliance on
manufacturer-controlled evidence.
As to Roundup, EPA has made no findings about
whether the formulated product causes cancer. In
2017, the agency determined that it could not reach “a
conclusion regarding the association between glyphosate exposure and risk of [non-Hodgkin lymphoma].”
Off. of Pesticide Programs, EPA, Revised Glyphosate
Issue Paper: Evaluation of Carcinogenic Potential 68
(Dec. 12, 2017). The data were uncertain partly
because “farmers and other applicators apply formulations, not the active ingredient alone.” Id. at 137
(emphasis added). So EPA acknowledged the need
for more research “to determine whether formulation
12
components, such as surfactants, influence the toxicity of glyphosate formulations.” Id. at 144. Even so,
in January 2020, EPA determined that “glyphosate is
not likely to be carcinogenic to humans.” NRDC, 38
F.4th at 43. The Ninth Circuit vacated that conclusion as “the hallmark of arbitrary action.” Id. at 51.
The agency’s treatment of paraquat followed a similar pattern. Paraquat was first registered in 1964,
before EPA existed; EPA classified it as a restricteduse pesticide in 1978 but never required neurotoxicity
testing—then cited the absence of such testing as
proof of safety. Patterson.Dep. 31, 89-90; 43 Fed. Reg.
5782. Successive reevaluations reached the same
circular conclusion. See, e.g., EPA, Reregistration
Eligibility Decision (RED) Paraquat Dichloride 33
(Aug. 1997); Shelley DuTeaux et al., Cal. Dep’t of Pesticide Regulation, Preliminary Report of the Potential
Human Health Outcomes Resulting from Paraquat
Exposure 16-17 (Dec. 2024) (“DuTeaux, Preliminary
Report”).
Syngenta reinforced that vacuum by keeping critical
voices off EPA’s Scientific Advisory Panel. In 2005,
the company orchestrated opposition to a researcher’s
nomination “with care” so the effort “cannot be
attributed to Syngenta.” Botham.Dep. 675-81, 685-89,
696. In 2013, Syngenta told EPA that paraquatrelated brain cell loss without disclosing the Marks
studies “was not reproducible”; in 2017, it told EPA
“There are No Effects of Paraquat in Animal Models”—a statement a corporate designee conceded
“would not be correct as written.” Dixon.Dep. 208,
211-18, 236-37, 242-44. EPA’s 2019 systematic review
considered only 11 of 217 identified animal studies,
finding “limited, but insufficient epidemiologic
evidence.” EPA, Paraquat Dichloride: Systematic
Review 4-5, 89 (June 26, 2019). Its 2021 Interim
13
Decision imposed new restrictions but again declined
to address Parkinson’s. EPA, Paraquat Dichloride:
Interim Registration Review Decision 17-18 (July
2021).
Independent actors have attempted to fill these
gaps. In 2015, a working group at the International
Agency for Research on Cancer—whose assessments
“are generally recognized as authoritative,” Fed. Jud.
Ctr., Reference Manual on Scientific Evidence 20, 564
n.46 (3d ed. 2011)—concluded glyphosate probably is
carcinogenic to humans. RA48 (¶ 50). California then
categorized glyphosate as a chemical known to cause
cancer. In April 2022, EPA wrote it “could approve” a
California-proposed warning informing consumers
that “[IARC] classified glyphosate as probably carcinogenic to humans” while “US EPA has determined
that glyphosate is not likely to be carcinogenic to
humans.” RA57. That letter has been withdrawn.
California likewise has regulated paraquat since
1974. See DuTeaux, Preliminary Report 17. Agricultural use requires a county-issued permit and is
subject to restrictions on aerial spraying and use near
schools and residences. See Cal. Code Regs. tit. 3,
§§ 6420(a), 6466, 6470; Cal. Food & Agric. Code
§§ 14001-14015. At least 10 States have considered
or adopted measures to ban or restrict paraquat. See
Am. Parkinson Disease Ass’n, Paraquat is banned in
70+ countries, but still legal in the US (Feb. 24, 2026).
4. Soon after IARC concluded glyphosate probably
causes cancer, thousands of Roundup-exposed plaintiffs brought actions consolidated in a federal MDL.
In 2021, Monsanto’s parent company, Bayer,
announced that it would discontinue glyphosatebased Roundup products for the residential market.
Although farmers continue to use glyphosate-
14
containing Roundup, Monsanto claims it has used
different active ingredients in consumer Roundup
since 2023.
In February 2026, Monsanto proposed a nationwide
settlement binding all persons who bought, applied,
or even saw Roundup applied in the United States,
but excluding judgments now on appeal. Class Action
Settlement Agreement §§ 2.1, 2.1(b)(iii), King v. Monsanto Co., No. 2622-CC00325 (Mo. Cir. Ct. Feb. 17,
2026). After preliminary approval in March, Bayer
explained that this Court’s review would affect only
“outstanding damage awards subject to pending
appeals, which are not covered by the settlement.”4
That universe consists of two cases—this one and
Monsanto Co. v. Anderson, No. 25-1042 (U.S.).
Paraquat applicators have pursued parallel protections through state-law litigation, bringing claims
including failure to warn. In 2021, the Judicial Panel
on Multidistrict Litigation centralized the federal
actions in the Southern District of Illinois. The
district court largely has denied defendants’ motions
to dismiss, including on preemption. On March 3,
2026, Syngenta announced that it would cease global
production of paraquat as of June 2026.
4 Bayer, Missouri court grants preliminary approval of
Roundup™ class settlement to resolve current and future claims
(Mar. 4, 2026).
15
ARGUMENT
I. FIFRA DOES NOT EXPRESSLY PREEMPT
LABEL-BASED FAILURE-TO-WARN CLAIMS
Express preemption turns primarily on “the language of the pre-emption statute and the statutory
framework surrounding it.” Medtronic, Inc. v. Lohr,
518 U.S. 470, 486 (1996) (cleaned up); see Carson v.
Monsanto Co., 72 F.4th 1261, 1267 (11th Cir. 2023) (en
banc). FIFRA “authorizes a relatively decentralized
scheme that preserves a broad role for state regulation.” Bates, 544 U.S. at 450. “Most significantly,
States may ban or restrict the uses of ” EPA-approved
pesticides, and they may register pesticides for uses
beyond those approved by EPA. Id. (citing § 136v(a),
(c)); see also § 136w-1 (granting States primary enforcement responsibility for use violations).
That framework accommodates state-law failure-towarn claims based on inadequate labeling, even where
EPA has not required the warning. Monsanto’s and
the government’s contrary arguments reflect a misunderstanding of both FIFRA’s allocation of regulatory authority and state failure-to-warn law.
A. Failure-To-Warn Claims Like Respondent’s
Are Consistent With FIFRA, Which Reserves
Significant Authority To States
1. FIFRA expressly delegates States “authority”
to “regulate” the “sale or use of any federally registered pesticide,” except that States may not permit
what federal law prohibits. § 136v(a). FIFRA also
authorizes State registrations of pesticides to accommodate “special local needs,” and such registration
“shall authorize distribution and use only within such
State.” § 136v(c)(1).
16
That affirmative authorization for States to regulate “use[s]” encompasses state tort claims, which
supplement federal and state pesticide regulations.
Although FIFRA itself “does not provide a federal
remedy to [those] who are injured as a result of a
manufacturer’s violation of FIFRA’s labeling requirements, nothing in § 136v(b) precludes States from
providing such a remedy.” Bates, 544 U.S. at 448.
There is a “long history of tort litigation against manufacturers of poisonous substances.” Id. at 449-51.
This Court thus observed that “[p]rivate remedies
that enforce federal misbranding requirements would
seem to aid, rather than hinder,” FIFRA’s functioning.
Id. at 451.
As this Court concluded in Bates, § 136v(b) does not
expressly preempt state common-law suits. That
“narrow” preemption provision, id. at 452, “prohibits
only state-law labeling and packaging requirements
that are ‘in addition to or different from’ the labeling
and packaging requirements under FIFRA,” id. at 447
(quoting § 136v(b)) (emphasis in Bates). It “calls for
an examination of the elements of the common-law
duty at issue.” Id. at 445. For a state tort claim to
be preempted, it must set forth (1) “a requirement
‘for labeling or packaging’ ” (2) “that is ‘in addition to
or different from’ ” one of FIFRA’s requirements. Id. at
443-44 (quoting § 136v(b)) (emphases in Bates).
The preemption inquiry thus proceeds in two steps.
Courts first ask whether a state-law claim imposes
any requirement for pesticide labeling or packaging.
“A requirement is a rule of law that must be obeyed.”
Id. at 445. Claims that would not require manufacturers to “label or package their products in any
particular way” are not preempted. Id. at 444; see id.
(“petitioners’ claims for defective design . . . are not
17
pre-empted”). For example, Bates found it “perfectly
clear” that common-law claims “that require manufacturers to design reasonably safe products” and “use
due care in conducting appropriate testing of their
products” are not preempted. Id.
Next, courts ask whether the state-law labeling
requirement is “in addition to or different from those
required under [FIFRA].” § 136v(b). Common-law
duties are not preempted if they are “equivalent to,
and fully consistent with, FIFRA’s misbranding provisions” and the “relatively few regulations that refine
or elaborate upon FIFRA’s broadly phrased misbranding standards.” Bates, 544 U.S. at 447, 453 n.28;
see id. at 454 (“[A] manufacturer should not be held
liable under a state labeling requirement subject to
§ 136v(b) unless the manufacturer is also liable for
misbranding as defined by FIFRA.”). In other words,
FIFRA does not preempt state-law claims that impose
“parallel requirements” to those in FIFRA. Id. at 447.
2. FIFRA does not expressly preempt state-law
failure-to-warn claims where EPA has not imposed
specific warnings. First, such claims are a permissible
exercise of the state authority to regulate pesticide use
that § 136v(a) preserves. Under FIFRA’s decentralized scheme, EPA is not the final arbiter of how pesticides may be used—States are. Section 136v(a) provides that “[a] State may regulate the sale or use of
any federally registered pesticide or device in the
State.” That authority is sweeping: it includes the
power to ban a federally registered pesticide outright,
even one EPA considers properly labeled. See Bates,
544 U.S. at 446. And FIFRA confers on States
“primary enforcement responsibility” for pesticide use
violations. § 136w-1. Because FIFRA does not dictate
how pesticides must be used, state-law requirements
18
governing use do not impose requirements “in addition to or different from” any federal use requirement.
State failure-to-warn claims operate within that
preserved authority, at least where a manufacturer
could have satisfied its duty by informing users
how to use the product safely. Here, for example,
Monsanto could have provided Durnell PPE instructions like those it gives to agricultural users. See
5 Tr. 3423:13-15 (“Monsanto gives the most stringent
warnings to the most sophisticated users.”). Durnell
testified he would have heeded them. 4 Tr. 2508:162509:19. A warning instructing a consumer to wear
gloves when spraying a weedkiller is a use instruction
that must, as a practical matter, appear on the label.
It thus falls within the state authority § 136v(a) preserves without being negated by the limited carveout
of § 136v(b).
This Court confronted a closely related issue in
Bates, where “Congress [had] amended FIFRA to
allow EPA to waive efficacy review of newly registered
pesticides.” 544 U.S. at 450. The Court held that
this gap in federal oversight did not preempt statelaw claims, explaining that it was “unlikely that Congress considered a relatively obscure provision like
§ 136v(b) to give pesticide manufacturers virtual immunity from certain forms of tort liability,” including
the efficacy-related claims there. Id. The same logic
applies here: EPA’s lack of final authority over use is
a reason to preserve state authority, not to preempt it.
Second, nothing in FIFRA prohibits a State from
requiring additional warnings to address state or local
concerns, so long as those requirements do not result
in labeling that is “in addition to or different from”
federal requirements. Where a warning requirement
19
can be implemented through nationally uniform labeling, § 136v(b) is not implicated: “EPA approves only
one label per pesticide,” and, “[i]n approving a labeling
change, EPA substitutes a new nationally uniform
label.” Brief Amicus Curiae for the United States in
Support of Plaintiffs-Appellants 17, Etcheverry v. TriAg Serv., Inc., 993 P.2d 366 (Cal. 2000) (No. S072524,
filed Mar. 1999). Thus, even state-specific instructions are routinely reflected in manufacturers’ nationally uniform labeling. See Bates, 544 U.S. at 435 (noting supplemental label for Strongarm applicable in
New Mexico, Oklahoma, and Texas); infra p.27.
Third, even apart from § 136v(a), state-law warning
claims are not preempted because—at most—they
impose parallel requirements to FIFRA’s. As the
court of appeals observed, “Missouri’s strict liability
failure to warn cause of action is fully consistent”
with FIFRA’s requirements. Pet.App.6. The same is
true of failure-to-warn causes of action under other
States’ law. See, e.g., Carson v. Monsanto Co., 92
F.4th 980, 992 (11th Cir. 2024) (Georgia); Hardeman
v. Monsanto Co., 997 F.3d 941, 955 (9th Cir. 2021)
(California). These claims are “equivalent to, and fully
consistent with, FIFRA’s misbranding provisions,”
Bates, 544 U.S. at 447, not preempted.
Bates instructs that courts weighing claims of parallel requirements examine the elements of the claim.
See id. at 445; id. at 456-57 (Thomas, J., concurring in
the judgment in part and dissenting in part). Here,
Durnell first had to prove at trial that Monsanto failed
to “give an adequate warning of the danger” posed by
Roundup. Pet.App.6. That duty tracks § 136(q)(1)(G),
which requires a warning “necessary” and “adequate
to protect health.”
20
Durnell’s claim also requires warnings in narrower
circumstances than FIFRA does.5 FIFRA requires
adequate safety warnings no matter the consumer’s
knowledge. § 136(q)(1)(G). Missouri requires a warning only if the product is “unreasonably dangerous
when put to a reasonably anticipated use without
knowledge of its characteristics.” 5 Tr. 3378:19-21;
see Moore v. Ford Motor Co., 332 S.W.3d 749, 756 (Mo.
2011); JA159-60 (jury instruction).
Durnell’s failure-to-warn claim thus functionally
enforces FIFRA’s misbranding prohibition. “[A] state
cause of action that seeks to enforce” FIFRA “ ‘does not
impose a requirement that is “different from, or in
addition to,” requirements under federal law,’ ” and so
is not preempted. Bates, 544 U.S. at 447-48 (quoting
Lohr, 518 U.S. at 513 (O’Connor, J., concurring in part
and dissenting in part)).
B. Monsanto’s Express-Preemption Arguments
Lack Merit
Monsanto’s cornerstone argument is that EPA’s
decision to register a pesticide and approve its label
imposes a preemptive “requirement” under FIFRA.
That argument always has been incorrect, but it is
even less persuasive now that the Ninth Circuit has
vacated the reasoning EPA used when registering
glyphosate and EPA has not challenged that vacatur.
1. After an 11-year re-registration process that
began in 2009, EPA failed to sustain its initial view
that glyphosate was not likely to cause cancer.
The Ninth Circuit held that EPA lacked substantial
evidence for that position and that its reasoning was
“the hallmark of arbitrary action.” NRDC, 38 F.4th at
51.
5 FIFRA does not expressly preempt “narrower” state requirements. Bates, 544 U.S. at 447 n.23.
21
Although glyphosate remains registered, any
preemptive effect of registration is nil. A vacated
agency decision has no legal effect. “In essence, a
vacatur order takes the unlawful agency action off the
books, which is an entirely appropriate response when
a plaintiff successfully establishes that the agency’s
conduct violates the law.” Kiakombua v. Wolf, 498 F.
Supp. 3d 1, 50 (D.D.C. 2020) (Jackson, J.) (cleaned up).
The D.C. Circuit therefore has vacated an agency
order because it “relied not only on [an already-vacated
order] but also on its defective reasoning.” WorldCom,
Inc. v. FCC, 246 F.3d 690, 696 (D.C. Cir. 2001).
EPA’s registration of glyphosate cannot support
preemption because its “defective reasoning” about
carcinogenicity has been vacated. Even so, Monsanto
cites (at 17, 31, 49) EPA’s statement that its “underlying scientific findings regarding glyphosate, including its finding that glyphosate is not likely to be
carcinogenic in humans, remain the same.” EPA, EPA
Withdraws Glyphosate Interim Decision (Sept. 23,
2022). That bare statement has no legal effect, much
less a preemptive one.
2. Even apart from the glyphosate-specific
vacatur, EPA’s registration and approval of labeling
cannot immunize a manufacturer from tort liability.
That conclusion flows from FIFRA’s text, structure,
and Monsanto’s own labeling practices.
Text. FIFRA provides explicitly in § 136a(f )(2) that
registration is only “prima facie evidence” that a
pesticide complies with the statute—that is, they are
“not final” but may be rebutted. United States v. ICC,
337 U.S. 426, 435 (1949). Registration thus is not “a
defense for the commission of any offense under
[FIFRA].” § 136a(f )(2).
22
Section 136a(f )(2) provides in full:
(2) Registration not a defense
In no event shall registration of an article be
construed as a defense for the commission of any
offense under [FIFRA]. As long as no cancellation
proceedings are in effect registration of a pesticide
shall be prima facie evidence that the pesticide, its
labeling and packaging comply with the registration provisions of [FIFRA].
Three conclusions follow. First, a pesticide can be
“registered but nevertheless misbranded.” Bates, 544
U.S. at 438. Second, EPA is not the ultimate arbiter
of whether labeling is adequate: even if the agency
approved a label, “a judge or jury” could “find that
[the] same label violates FIFRA.” Hardeman, 997
F.3d at 956; see Bates, 544 U.S. at 452 (“lay juries are
in no sense anathema to FIFRA’s scheme”). Third,
manufacturers have a continuing duty to update
labeling that is misbranded—retaining an EPAapproved but misbranded label is not a “requirement”
of FIFRA; it is a violation. Bates, 544 U.S. at 438.
A jury’s conclusion that an EPA-approved label
inadequately warned an injured plaintiff of the risks
is perfectly consistent with that scheme.
Structure. Statutory context reinforces that conclusion. First, the statute requires EPA to determine
whether manufacturer-drafted warnings are “necessary” and “adequate to protect [public] health” based
on manufacturer-submitted material. § 136(q)(1)(G);
see § 136a(c)(2), (c)(5)(B)-(D). Monsanto’s position
grants manufacturers immunity when labels they
draft are approved by EPA based on science they submit. No rational Congress would enact such a statute.
Second, as the United States previously informed
this Court, “EPA does not typically use the registra-
23
tion process to address [long-term] harms by requiring
chronic-risk warnings on a pesticide’s labeling.” U.S.
Hardeman Br. 11. The government now contends
(at 19 n.4) that EPA addresses chronic risks through
cancellation proceedings, but that is no answer. For
one thing, cancellation is rare: from 2010 to 2018,
EPA involuntarily cancelled just one pesticide registration. See Nathan Donley, The USA lags behind
other agricultural nations in banning harmful pesticides, 18 Envtl. Health #44, at 5-6 (2019).
For another, when EPA does act, the protracted
process is no substitute for adequate labeling. When
environmental groups petitioned EPA to cancel
chlorpyrifos’s registration in 2007, for example, EPA
“spent more than a decade” assembling a record and
employed “one delaying tactic after another.” League
of United Latin Am. Citizens v. Regan, 996 F.3d 673,
678 (9th Cir. 2021). Only after a Ninth Circuitimposed deadline did EPA ban chlorpyrifos on food
crops—and the Eighth Circuit then vacated that
ban as arbitrary and capricious. See Red River Valley
Sugarbeet Growers Ass’n v. Regan, 85 F.4th 881, 883
(8th Cir. 2023). After all that, chlorpyrifos remains on
the market.
Practice. If Monsanto were right (at 32-33) that
EPA-approved labels say exactly what is necessary to
protect human health—no more, no less—its own conduct would be inexplicable. The company has revised
Roundup’s labeling hundreds of times, including more
than 50 changes to the four products Durnell used.6
3. Monsanto’s counterarguments lack merit.
First, the company contends (at 38-39) that
§ 136a(f )(2) “is not a preemption provision at all.”
6 4 Tr. 2470:14-23, 2471:7-18, 2472:16-23, 2473:6-13; see
JA234-240.
24
But express preemption turns on “the language of
the pre-emption statute and the statutory framework
surrounding it.” Lohr, 518 U.S. at 486 (cleaned up,
emphasis added). Section 136a(f )(2)’s placement outside § 136v(b) is no reason to disregard it.
Because “EPA’s labeling determinations are not
dispositive of FIFRA compliance,” Monsanto offers
no basis to treat those determinations as any more
“conclusive as to which common law requirements are
‘in addition to or different from’ the requirements
imposed by FIFRA.” Hardeman, 997 F.3d at 956. Just
as a manufacturer with a registered pesticide still
may be liable for misbranding under FIFRA, it likewise may be subject to parallel liability under state
law. See Bates, 544 U.S. at 451 (discussing “[p]rivate
remedies that enforce federal misbranding requirements”).
Second, Monsanto leans heavily (at 39-40) on Riegel
v. Medtronic, Inc., 552 U.S. 312 (2008). But Riegel
involved the Medical Device Amendments (“MDAs”),
which operate differently from FIFRA.
The MDAs contain no provision like § 136a(f )(2),
which provides that registration is only “prima facie
evidence” of compliance, not proof that labeling is
“adequate to protect health,” § 136(q)(1)(F), (G). See
U.S. Hardeman Br. 18-19. The MDAs also reserve far
less power for States. Under FIFRA, States may ban
the sale or use of a pesticide outright. See § 136v(a).
The MDAs have no analogue.
More generally, the statutory schemes differ. The
MDAs “swept back” “state obligations” and “imposed
a regime of detailed federal oversight,” limiting States
from imposing nearly any condition “ ‘which relates to
. . . safety or effectiveness.’ ” Riegel, 552 U.S. at 316
(quoting 21 U.S.C. § 360k(a)(2)). FIFRA, by contrast,
25
“authorizes a relatively decentralized scheme that
preserves a broad role for state regulation.” Bates,
544 U.S. at 450 (citing § 136v(a)); see also § 136w-1
(conferring on States “primary enforcement responsibility”). Thus, “different federal statutes and regulations may . . . lead to different pre-emption results.”
PLIVA, 564 U.S. at 626.
Federal product review likewise differs. For medical
devices, “premarket approval is specific to individual
devices” and requires FDA to determine that the
device “offers a reasonable assurance of safety and effectiveness.” Riegel, 552 U.S. at 322-23. By contrast,
FIFRA’s misbranding provisions impose only “general
standards.” Bates, 544 U.S. at 453 n.27; see Lohr, 518
U.S. at 501 (no preemption where federal requirements “reflect[ed] important but entirely generic
concerns”). And EPA has acknowledged that it has
not evaluated glyphosate “formulations” like Roundup
and that, “if at any time[ ] information becomes available that indicates adverse human health effects of
concern for exposure to glyphosate or its formulations,
EPA intends to review it and determine the appropriate regulatory action.” Hardeman, 997 F.3d at 952
(cleaned up). EPA similarly has not evaluated paraquat’s Parkinson’s risks.
Third, Monsanto and the United States focus on a
“cancer warning.” That framing misapprehends state
failure-to-warn law and state use restrictions, which
do not turn on whether a manufacturer used a particular phrase. To avoid liability, Monsanto need not
have adopted a specific “cancer warning,” just as Syngenta need not adopt a specific “Parkinson’s disease
warning.” Rather, state law requires manufacturers
to provide “adequate instructions” and warnings to
reduce or avoid risks. Restatement (Third) of Torts:
Products Liability § 2 cmt. i (1998).
26
Here, the record reflects multiple ways Monsanto
could have satisfied that obligation. It could have
provided consumers like Durnell a PPE warning.
Or it could have added “links to relevant scientific
evidence and materials related to whether exposure to
Roundup Products causes [non-Hodgkin lymphoma].”
Class Action Settlement Agreement at PDF p.167, In
re Roundup Prods. Liab. Litig., No. 3:16-md-2741-VC,
ECF #12509-2 (N.D. Cal. Feb. 3, 2021).7 Monsanto
and the government ignore these options.
Fourth, Monsanto argues (at 36-38) that state-law
warnings would undermine national “uniformity.”
But Bates cautioned against “overstat[ing] the degree
of uniformity and centralization that characterizes
FIFRA,” explaining that the statute “authorizes a
relatively decentralized scheme that preserves a
broad role for state regulation.” 544 U.S. at 450.
To be sure, FIFRA’s preemption provision plays
“a narrow, but still important, role”: It promotes
uniformity in the presentation of labels—ensuring
that they use the same font, font size, color, and
similar features nationwide. It also bars state-law
requirements that conflict with the few specifically
listed federal ones. Id. at 452. Thus, a claim that
a label should have said “DANGER” rather than
“CAUTION” would be preempted where federal regulations specify those terms. Id. at 453 (citing 40 C.F.R.
§ 156.64).
No such federal requirement exists here. EPA has
not mandated or prohibited warnings about glyphosate’s chronic risks, just as it has not addressed
paraquat’s long-term neurotoxicity. FIFRA’s “narrow”
preemption provision therefore does not apply.
7 The district court rejected that settlement on other grounds,
and Monsanto never made that request of EPA.
27
Nor does real-world practice support Monsanto’s
uniformity concerns. Labels already incorporate
state-specific instructions. Roundup’s label directs
users to “requirements specific to your State or Tribe”
and to consult state regulators. BIO.App.30a. It also
includes aerial spraying restrictions in California and
Arkansas, BIO.App.35a-40a, and differing application
rates for sugarcane in Florida, Hawaii, Louisiana, and
Texas, BIO.App.42a-43a. Paraquat also is subject
to longstanding state-specific regulation. Supra p.13.
Monsanto complains (at 36-38) about 50 different
state labeling regimes, but never explains why it poses
a “uniformity” problem to offer state-specific instructions for sugarcane but not cancer on one label.
Finally, the government’s overwarning concern
has no merit. U.S. Br. 34 (citing Merck Sharp &
Dohme Corp. v. Albrecht, 587 U.S. 299, 304 (2019)).
Merck addressed prescription drugs—products whose
therapeutic benefits patients may need, and where
excessive warnings might deter necessary treatment.
No comparable concern exists here. A Roundup
consumer or paraquat applicator who chooses to wear
gloves or PPE, switch products, or pull weeds by hand
suffers no adverse health effect. The government thus
imports a concern about patients forgoing medication
into a context where the consequence is a change in
weed-management practices.
II. FIFRA DOES NOT IMPLICITLY PREEMPT
LABEL-BASED FAILURE-TO-WARN CLAIMS
The court of appeals also correctly held Monsanto
cannot show implied preemption. That “is a demanding defense.” Wyeth, 555 U.S. at 573. Before the court
below, the company did not even try to carry its heavy
burden: “The record contains no evidence that Monsanto either informed the EPA of the justifications
28
for a change to its warning label or that the EPA
has informed Monsanto it would not approve such a
warning.” Pet.App.9.
Here, Monsanto draws its implied-preemption arguments from prescription-drug cases under the Federal
Food, Drug, and Cosmetic Act. This Court conducts
an implied-preemption analysis in such cases because
Congress has “declined to enact [an express-preemption]
provision for prescription drugs.” Wyeth, 555 U.S. at
567. Those cases have dubious relevance here because
FIFRA has an express-preemption provision. See
Bates, 544 U.S. at 459 (Thomas, J., concurring in judgment in part and dissenting in part) (favorably noting
“this Court’s increasing reluctance to expand federal
statutes beyond their terms through doctrines of
implied pre-emption”). On their own terms, Monsanto’s
implied-preemption arguments lack merit.
1. Monsanto’s first implied-preemption theory
(at 43-47) rests on the premise that it could not add a
cancer warning to Roundup’s labeling without EPA’s
approval. That premise is false, and the arguments
that flow from it misread PLIVA.
In PLIVA, the Court addressed implied preemption
in the generic-drug context, where federal law
imposes a “duty of sameness” requiring generic labels
to match their brand-name counterparts. 564 U.S.
at 616. Because of that duty, generic manufacturers
cannot unilaterally change their labels—they only
may “ask the agency to work toward strengthening
the label” for both generic and brand-name drugs. Id.
Absent “the Federal Government’s special permission
and assistance” with the brand-name companies,
they cannot independently satisfy state-law duties
to provide adequate warnings. Id. at 623-24. That
constraint drove the Court’s holding: when federal
29
law affirmatively prohibits a manufacturer from
acting independently, state-law duties requiring such
action are preempted.
FIFRA could hardly be more different. First, it
places primary responsibility for labeling on the
manufacturer, not the agency. § 136a(c)(1)(C). When
label changes are necessary, the registrant drafts
and submits revised labeling to EPA, which “shall”
approve the change if it complies with FIFRA.
§ 136a(f )(1); 40 C.F.R. § 152.50(e). That process bears
little resemblance to the regime in PLIVA, which
depended on “a Mouse Trap game” of coordination
with brand-name manufacturers and afforded no
unilateral authority to the regulated party. 564 U.S.
at 619.
Second, pesticide registrants are not bound by
generic drugmakers’ “duty to keep the label the same.”
Id. at 618. Instead, they must abide by FIFRA’s duty
to keep the label current—that is, the “continuing
obligation to adhere to FIFRA’s labeling requirements.” Bates, 544 U.S. at 438.
Third, FIFRA differs further by permitting certain
label changes without prior EPA approval. Under
EPA regulations, registrants may implement specified
modifications through a notification process, subject
to later agency review. See 40 C.F.R. § 152.46(a); Off.
of Pesticide Programs, EPA, Pesticide Registration
Notice 98-10 (Oct. 22, 1998). Although Monsanto
responds (at 31) that adding a cancer warning would
not qualify for such treatment, “EPA has repeatedly
permitted pesticide manufacturers to use the notification procedure to add notices related to cancer to their
products’ labels.” Hardeman, 997 F.3d at 959. For
example, “Bayer CropScience notified EPA ‘of a minor
labeling amendment for LARVIN Technical,’ inform-
30
ing EPA that ‘as required by California Proposition
65, the following statement has been added to the
label, “This product contains a chemical known to
the state of California to cause cancer.” ’ ” Id. at 959
n.10 (cleaned up). Had Monsanto—now a Bayer subsidiary—taken the same approach here, it could have
prevented Durnell’s injuries.
2. Monsanto’s second theory (at 47) is that it
cannot add a “cancer warning” to Roundup labels
because EPA would not accept it. Again under the
FDCA, failure-to-warn claims are preempted when
there is “clear evidence” that FDA would not have
approved the warning that state law requires. Wyeth,
555 U.S. at 571. But “clear evidence” rests on “agency
actions taken pursuant to the [agency’s] congressionally delegated authority”: “notice-and-comment rulemaking,” an order “formally rejecting a warning
label,” or “other agency action carrying the force of
law.” Merck, 587 U.S. at 315-16.
There is no “clear evidence” showing Durnell’s
failure-to-warn claim is preempted. First, EPA has
promulgated no notice-and-comment-based regulation requiring certain warnings on glyphosate-based
product labels and barring others. Monsanto instead
points (at 49-50) to EPA’s 1993 Reregistration Eligibility Decision. EPA, Reregistration Eligibility Decision (RED) Glyphosate (Sept. 1993). But that decision
imposed labeling requirements only with respect to
water contamination and workplace safety; it did not
forbid the warnings at issue here. Id. at 72-73.
Second, EPA has taken no formal action rejecting a
warning adequate to prevent Roundup-caused harms,
and Monsanto never has asked for such a warning.
Third, EPA has taken no other action with the force
of law disapproving a state-law-required warning.
31
Monsanto cites (at 50) a 2019 letter from an EPA
employee concluding that glyphosate is “not likely
to be carcinogenic to humans” and that California’s
warning of glyphosate’s potential carcinogenic effects
was “false or misleading.” Pet.App.38-39. But the
company neglects to mention that every court to
consider this letter has held that it “did not carry
the force of law because it neither reflected sufficient
formality nor created a rule of law that must be
obeyed.” Carson, 92 F.4th at 996 (citation omitted);
see Hardeman, 997 F.3d at 957 (same).
Monsanto also says (at 50) that EPA’s decisions
declining to require a cancer warning—whether
through its registration review process or its approval
of individual labels—carry impossibility-preemptive
force. But this Court never has held that agency
silence can speak that loudly. See Sprietsma v.
Mercury Marine, 537 U.S. 51, 67-68 (2002) (agency
decision not to regulate does not preempt state
common-law claims).
III. MONSANTO’S POSITION WOULD HAVE
SUBSTANTIAL NEGATIVE EFFECTS
Monsanto’s position would bar essentially all failureto-warn claims based on a pesticide’s “labeling.” Such
immunity for pesticide manufacturers would hinder
FIFRA itself. As this Court observed in Bates, statelaw tort actions “may aid in the exposure of new
dangers associated with pesticides,” giving manufacturers “added dynamic incentives to continue to keep
abreast of all possible injuries stemming from use of
their product so as to forestall such actions through
product improvement.” 544 U.S. at 451. That’s true
for consumers who have used Roundup products for
decades around their homes and neighborhoods. And
the same is true for plaintiffs in the Paraquat MDL,
32
whose lengthy exposure to small doses of the pesticide
left them with Parkinson’s. Their extended exposure
can help inform EPA about the long-term effects of
pesticides and aid the agency in carrying out “its task
of assessing the environmental and health dangers
posed by” poisonous substances. Id. at 440.
That task is exceptionally important. Rather than
test formulated Roundup for long-term cancer risks
or provide warnings, Monsanto instead has waged a
decades-long campaign to mislead the scientific community and the public about the weedkiller’s cancer
risks. Syngenta likewise carried out a protracted campaign of misinformation—one deliberately aimed at
influencing EPA itself. Supra pp.9-11. Those efforts
came to light through litigation, not EPA’s oversight.
These companies’ practice of hiding their products’
defects shows why the proper scope of FIFRA preemption matters. As the United States once informed this
Court, there is “the possibility that the manufacturer’s
submissions to EPA may be inaccurate or incomplete,
or that evolving science will cast doubt on the
adequacy of approved labeling.” U.S. Hardeman Br.
12 n.3. If FIFRA preempted the very suits that expose
those deficiencies, manufacturers could profit from
their own nondisclosure. Regulatory silence—some of
it of their own making—would become a shield
against accountability.
Bates rejected that result, and rightly so. Congress
has not disturbed Bates, and Monsanto does not ask
this Court to overrule it. If FIFRA does not preempt
state-law suits for crop damage, it surely does not
preempt suits for grievous injury and death.
CONCLUSION
The state court of appeals’ judgment should be
affirmed.
33
Respectfully submitted,
ROBIN L. GREENWALD
WEITZ & LUXENBERG P.C.
700 Broadway
New York, NY 10003
(212) 558-5500
KHALDOUN A. BAGHDADI
WALKUP, MELODIA, KELLY
& SCHOENBERGER
650 California Street
26th Floor
San Francisco, CA 94108
(415) 212-4350
March 31, 2026
DAVID C. FREDERICK
Counsel of Record
DEREK C. REINBOLD
KYLE B. GRIGEL
ALYSSA J. PICARD
KELLOGG, HANSEN, TODD,
FIGEL & FREDERICK,
P.L.L.C.
1615 M Street, N.W.
Suite 400
Washington, D.C. 20036
(202) 326-7900
(dfrederick@kellogghansen.com)
This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.