Is It Hot In Here Or Is It Just California? With Latest Proposed Changes To The Cartwright Act, California Aims To Turn Up The Heat On Monopolies.

The Cartwright Act, California’s state antitrust law, has never had an equivalent to Section 2 of the Sherman Act that would allow state authorities to target single-firm monopolization conduct. That appears likely to change this year. California recently got one step closer to enacting legislation that would significantly extend the scope of the state’s antitrust laws to target not just anticompetitive conspiracies but also monopolization — and on broader terms than federal law operates. 

On May 27, the California Assembly voted to pass the COMPETE Act, which would amend the Cartwright Act to apply to conduct by “one or more persons” and explicitly decouple it from federal case law interpreting the Sherman Act. The bill now heads to the state Senate, which has until August 31 to advance it to Gov. Gavin Newsom. If the COMPETE Act passes, it would go into effect in 2027. 

California has already broadened its antitrust laws twice in recent months, as it seeks to step up state-level antitrust enforcement in the face of a perceived federal pullback. In addition to clarifying the Cartwright Act’s more liberal pleading standards, California enacted legislation in October 2025 that restricted the use of common pricing algorithms and significantly increased financial penalties for criminal and civil violations. And in February of this year, Newsom signed the California Uniform Antitrust Premerger Notification Act, which establishes a premerger notification regime for California, distinct from the federal Hart-Scott-Rodino process. 

If the COMPETE Act in its current form becomes law, it will significantly change the antitrust landscape for businesses in California:

• A separate grounds for going after single-firm conduct. State attorneys general (AGs) already have the authority to bring monopolization cases under federal law, but the COMPETE Act would permit the California AG also to add corresponding state law claims for the same conduct under the Cartwright Act. Doing so would not be simply about piling on but, in light of some of the other recent and proposed changes discussed further below, would increase the AG’s chances of victory. 
• What is the sound of one hand restraining trade? In adding single-firm conduct to the Cartwright Act, the California Legislature chose not to alter the “restraint of trade” language in the statute, which previously (and has historically in antitrust) described anticompetitive conduct between multiple firms. It is not clear if that was a drafting error or, if not, what sort of unilateral conduct might “restrain trade” under the Cartwright Act. If this language persists in the final law, it will create significant uncertainty for businesses as litigants and courts grapple with its meaning. 
• California’s more liberal pleading standards lower the burden for stating a monopolization claim. As of January 1, the Cartwright Act explicitly has a more liberal pleading standard than the Sherman Act. To survive dismissal, plaintiffs don’t have to meet the heightened Twombly-Iqbal standard that applies to federal claims; they only have to allege facts that make a restraint of trade “plausible.” 
• Disclaiming federal antitrust case law. The California Supreme Court has already held that the Cartwright Act is “broader in range and deeper in reach” than the Sherman Act. But the COMPETE Act goes further (and has been proposed in a number of federal antitrust bills that have not proceeded), expressly removing or modifying elements of various court-fashioned doctrines. This includes not requiring a prior profitable course of dealing to prove a refusal to deal as required by Trinko, dispensing with the need under AmEx to show harms on both sides of a two-sided market in order to demonstrate an anticompetitive effect, and eschewing market definition altogether when relying on direct evidence of market power, among others. All these changes together would have the effect of making Cartwright Act monopolization claims easier to bring and win than Sherman Act claims and would complicate litigation strategy in cases that feature claims under both laws. 

Expansion of state antitrust laws such as the COMPETE Act go hand in hand with the more aggressive enforcement of existing antitrust laws by state AGs in recent years. Businesses ignore these state-level antitrust developments at their own risk because California (among other states) is plainly ready to hold their feet to the fire.