Federal Court Permanently Enjoins Prop 65 Cancer Warnings for DEA in Cosmetics

A federal court in the Eastern District of California has permanently barred the California Attorney General from enforcing Proposition 65’s cancer warning requirement for diethanolamine (DEA) in cosmetics and personal care products. The order, entered June 23, 2026, in The Personal Care Products Council v. Bonta, is the fourth time in recent years that a federal court has enjoined a requirement to provide Proposition 65 warnings on First Amendment grounds, following earlier victories involving glyphosate, acrylamide, and titanium dioxide. Industry groups now have a fairly consistent playbook for attacking Proposition 65 warnings based on disputed science, and the state’s Attorney General is increasingly declining to defend against such challenges.

Background

Proposition 65 requires businesses to warn before knowingly exposing anyone in California to a chemical the state has listed as “known to the state to cause cancer or reproductive toxicity.” Cal. Health & Safety Code § 25249.6. Under the so-called “Labor Code mechanism,” if the International Agency for Research on Cancer (IARC) classifies a chemical as a known human carcinogen, or a probable or possible human carcinogen with “sufficient evidence” of carcinogenicity in animals, California’s Office of Environmental Health Hazard Assessment (OEHHA) must automatically add it to the Proposition 65 list, without any independent scientific review. Penalties for noncompliance can reach $2,500 per violation, per day. Proposition 65 also allows private citizens “acting in the public interest” to file lawsuits to enforce the warning requirement, so long as they first serve a 60-day notice of violation on the business, the Attorney General, and local prosecutors. If none of those officials elects to file a suit in that window, the private plaintiff can step into the shoes of the state and proceed on the state’s behalf. Private plaintiffs have strong incentives to pursue such claims because they are entitled to keep a share of the penalties ultimately recovered. Indeed, a substantial majority of Proposition 65 suits are brought by private citizens rather than the Attorney General.

DEA is an organic compound used as a surfactant, emulsifier, and pH adjuster in a wide range of consumer products, including shampoos, conditioners, hair gels and dyes, shaving gels, makeup, lotions, and sunscreens. It was added to the Proposition 65 list in June 2012 after IARC concluded that DEA was “possibly carcinogenic to humans.” Notably, neither OEHHA nor any federal or California state agency has ever independently concluded that DEA is linked to cancer in humans.

The PCPC Lawsuit Challenging DEA’s Inclusion in Prop 65 List

The Personal Care Products Council (PCPC), the trade association for cosmetics and personal care product manufacturers, sued Attorney General Rob Bonta in March 2026 under 42 U.S.C. § 1983, arguing that a Proposition 65 warning regarding DEA was based on only a single study that found a possible cancer link in a strain of mice known to be particularly prone to cancer. PCPC argued that this warning requirement forces its members to make false and misleading statements about their DEA-containing products.

The PCPC case follows a similar legal theory to the glyphosate case (National Association of Wheat Growers v. Bonta), the acrylamide case (California Chamber of Commerce v. Bonta), and PCPC’s own earlier titanium dioxide case (Personal Care Products Council v. Bonta), in which industry groups challenged Proposition 65’s warning requirements as unconstitutional compelled speech under the First Amendment, on the theory that a warning resting on unsettled or contested science cannot be purely factual or uncontroversial. Government-mandated commercial disclosures ordinarily need only be “purely factual and uncontroversial” to survive a relaxed form of First Amendment review that applies specifically to disclosure requirements, rather than the more stringent scrutiny that governs other compelled or restricted commercial speech. Zauderer v. Office of Disciplinary Counsel of the Supreme Court of Ohio, 471 U.S. 626, 651 (1985). A warning ceases to be purely factual when it asserts a health risk that is not fully established in the scientific community. Where the science is not well established, courts apply the more stringent intermediate scrutiny standard, which requires the government to show that the compelled speech directly advances a substantial interest without being broader than necessary. Nat’l Ass’n of Wheat Growers v. Bonta, 85 F.4th 1263, 1283 (9th Cir. 2023) (applying Central Hudson Gas & Electric Corp. v. Public Service Commission of New York, 447 U.S. 557, 566 (1980)).

PCPC’s complaint made three linked arguments with respect to the DEA warning. First, the warning is not a neutral fact but a compelled false statement — it requires businesses to tell customers that a product can expose them to a chemical known to cause cancer, which PCPC argued is not true. Second, the science behind adding DEA to the Proposition 65 list is too thin because it is based only on a single study in a cancer-prone mouse strain. A parallel rat study did not find the same link, and no human study has independently concluded that DEA is linked to cancer in humans. Third, because the warning is not purely factual and uncontroversial, the more lenient Zauderer standard does not apply, and the warning also fails the more stringent level of First Amendment scrutiny because the state has no legitimate interest in forcing a false or misleading warning on a product label.

Impact of the Order

Rather than litigate the case to a merits ruling, Attorney General Bonta and PCPC entered into a stipulated judgment. Judge Daniel J. Calabretta of the Eastern District of California, Sacramento Division, signed the resulting Order Regarding Final Judgment and Permanent Injunction on June 23, 2026. The Order provides the following relief:

• Permanently enjoins the Attorney General, and anyone acting in privity or concert with him, from filing or prosecuting new Proposition 65 suits over DEA in cosmetics and personal care products
• Declares that, given the current state of the science, the Proposition 65 cancer warning requirement for DEA cannot be enforced consistent with the First Amendment
• Allows the Attorney General to move under Rule 60(b)(5) or (6) to dissolve the injunction if the facts or the law change
• Keeps the case open so the court can enforce the injunction going forward
• Enters judgment for PCPC, with each side covering its own fees and costs

Notably, Attorney General Bonta did not concede the constitutional argument. The stipulation states he still disputes that the DEA warning violates the First Amendment, but explains that both sides evaluated the current science, the reasoning courts used in the glyphosate, acrylamide, and titanium dioxide cases, and the governing precedent, and concluded that a stipulated judgment was the sensible way to resolve the case.

Practical Takeaways

The injunction is limited to DEA in cosmetics and personal care products and does not cover DEA exposures posed by other products. But within that scope, the injunction should bar both AG-led enforcement and the private citizen enforcement suits that make up the bulk of actual Proposition 65 litigation.

Read alongside the glyphosate, acrylamide, and titanium dioxide cases, the DEA order gives industry groups an established blueprint to challenge Proposition 65 warning requirements. When a chemical is listed under Proposition 65 based solely on an IARC determination that the chemical is a “probable” or “possible” carcinogen without direct evidence that the chemical is linked to cancer in humans, industry groups will likely sue, and a federal court — or the state itself, by stipulation — could conclude that the warning is based on evidence too shaky to survive First Amendment scrutiny. We expect industry groups to continue challenging chemicals on the Proposition 65 list that fall into this category.

© Arnold & Porter Kaye Scholer LLP 2026 All Rights Reserved. This Advisory is intended to be a general summary of the law and does not constitute legal advice. You should consult with counsel to determine applicable legal requirements in a specific fact situation.