The California Law Revision Commission has released draft legislative changes that could significantly expand the scope of the state’s Cartwright Act. The proposed amendments would, for the first time, apply the Cartwright Act to exclusionary unilateral (single-firm) conduct, in addition to anticompetitive agreements already covered by the law. If adopted, these changes could make it easier for plaintiffs to bring single-firm conduct cases under California law.
Currently, the Cartwright Act applies only to conduct involving “two or more persons,” which means it does not address unilateral conduct. The Commission’s proposal would extend liability to single-firm actions such as refusals to deal, bundled discounts, and exclusionary pricing—areas where federal courts have traditionally imposed significant limitations.
The California Legislature requested in 2022 that the Commission study whether state antitrust laws should be amended to include single-firm conduct. A working group presented a preliminary report in 2024; public comments were received in 2025; and a draft final report was published on January 20, 2026. The proposed amendments would set new legal standards that depart from federal monopolization law under Section 2 of the Sherman Act.
The proposal is part of a broader trend among states diverging from federal antitrust standards. For example, after the Supreme Court’s Illinois Brick decision limited indirect purchasers’ ability to bring claims, many states changed their laws to allow such claims. Other states have enacted their own merger notification statutes and maintained stricter rules against certain pricing practices even as federal law has relaxed them.
Under the draft legislation, three new sections would be added to the Cartwright Act. Section 16730 outlines that California’s law is more expansive than its federal counterpart—a provision courts could use for broader interpretation. Section 16731 prohibits single firms from monopolizing or monopsonizing markets or attempting either action. This section explicitly addresses monopsony (buyer-side market power), with implications for labor and other markets.
Section 16732 introduces ten factors that federal courts often require for establishing liability under Section 2 of the Sherman Act but would not make any of them prerequisites under California law. These factors relate to refusals to deal, exclusionary pricing practices like predatory or bundled pricing, treatment of two-sided markets (such as digital platforms), and other aspects of competition analysis.
For instance, unlike current federal standards established by Supreme Court decisions such as Trinko and Brooke Group, plaintiffs under the revised Cartwright Act would not need to prove a prior course of dealing or below-cost pricing in refusal-to-deal or predatory pricing cases. In bundled discount cases, plaintiffs would not have to show they are as efficient as defendants—relaxing requirements set by previous court rulings.
In two-sided market scenarios (like credit card networks), California’s proposal rejects the need for plaintiffs to prove harm across both sides of a platform—a departure from Supreme Court precedent in American Express.
Additional changes include relaxing requirements around proving discrimination between customers or defining relevant markets when there is direct evidence of competitive harm. Market share thresholds used in federal cases might also become less important under state law if these amendments pass.
The Commission is reviewing these proposals alongside potential reforms concerning mergers and artificial intelligence. At its meeting on March 20, 2026, it will consider whether to adopt its draft recommendations; if so adopted, they will go before the Legislature and potentially then Governor Gavin Newsom for enactment into law. Historically, over ninety percent of Commission recommendations have been enacted by lawmakers.
If implemented, these changes could substantially affect how companies with large market shares operate in California and beyond due to California’s economic size and influence. Private parties and state officials alike could pursue single-firm conduct claims more easily under state law than under current federal standards.
“WilmerHale’s leading antitrust team in California and around the world is ready to assist you with planning for and responding to these crucial potential Cartwright Act developments. We are also prepared to discuss ways in which interested firms might participate in the Commission’s and potentially the Legislature’s evaluation of the proposal.”