California Antitrust & Cartwright Act

California runs its own competition regime, and it diverges from federal antitrust law in ways that decide cases — who can sue, what conduct is per se unlawful, what a merger filing requires, and, from 2027, what single-firm conduct the State can prosecute. Bona Law is an antitrust boutique headquartered in San Diego that litigates and counsels under the Cartwright Act, the Unfair Practices Act, and the Unfair Competition Law every day, for plaintiffs and defendants alike. The California Attorney General's Office retained Bona Law as outside trial counsel to prosecute Cartwright Act and UCL claims against global gasoline trading firms in People v. Vitol — an action that resolved in a $50 million settlement — and our partners include the former senior Deputy Attorney General who led that case for the State. The firm is recognized in the Chambers Spotlight 2026 California Guide for antitrust — a ranking it also holds in New York.

Representative California Experience

People v. Vitol Inc., et al. (S.F. Super. Ct.). Served as outside trial counsel for the California Attorney General's Office in a Cartwright Act and UCL action against global gasoline trading firms alleged to have manipulated California gasoline price indices; resolved in a $50 million settlement — an engagement that reflected the unusual posture of a state attorney general retaining a private antitrust boutique to prosecute the State's claims. Read more on our energy and commodities trading page.
AmeriCare MedServices v. City of Anaheim, et al. (C.D. Cal.; Ninth Circuit; U.S. Supreme Court cert petition). Prosecuted twelve antitrust actions against Orange County municipalities over monopolized ambulance markets — the litigation that anchors our national practice on antitrust challenges to government action.
San Diego Association of Realtors v. Sandicor (S.D. Cal.). Prosecuted a Section 1 conspiracy action against the regional MLS; the court sustained the antitrust claims over motions to dismiss. See our real estate and housing practice.
In re Capacitors Antitrust Litigation (N.D. Cal.). Defeated indirect-purchaser class certification for our then-client Taitsu in one of the decade's largest electronics price-fixing MDLs, on California choice-of-law grounds.
Summary judgment victory for Foster Farms (July 2026), the California-based poultry processor, in the nationwide turkey price-fixing MDL. See our agriculture and food practice.
Ariix v. NutriSearch (S.D. Cal.; Ninth Circuit). Argued and won the appeal reinstating a Lanham Act false-advertising claim over rigged "independent" supplement ratings, producing a precedential Ninth Circuit decision on commercial speech. See our Lanham Act and false advertising practice, our analysis of the reach of Ariix, and our explainer on suing over fake reviews and rigged "independent" ratings.
People v. Enayati (L.A. Super. Ct.). Defending a Santa Monica property owner in the City of Santa Monica's enforcement action under the UCL and False Advertising Law — apparently the first attempt by a California city to use those statutes to enforce a local rental ordinance — on Costa-Hawkins preemption, Coastal Act, and city-charter grounds. Read more.
Defense of a major egg producer in class actions alleging violations of state price-gouging laws, and a group-boycott action in Napa and Solano counties.
California counseling engagements, including licensing-board antitrust issues, MAP and distribution programs under California law, single-firm conduct and market-power assessments, and privacy-adjacent demand-letter defense for consumer-products companies.

Our California Antitrust Team

Ten Bona Law attorneys are admitted to the State Bar of California:

Paul Moore — Partner. Former DOJ Antitrust Division trial attorney and former senior California Deputy Attorney General. He has created investigative plans, developed teams of lawyers and cross-functional teams (including forensic accountants, economists, industry experts, and financial analysts), and led substantial merger, conduct, and compliance investigations on behalf of the government — including multi-agency investigations and initiating and litigating law enforcement actions and merger challenges. Author of the firm's analysis of the COMPETE Act and of Inside State Enforcement.
Jarod Bona — Founder and CEO. Harvard Law School; Eighth Circuit law clerk; previously antitrust litigation at DLA Piper and Gibson Dunn; founder and editor of The Antitrust Attorney Blog.
Jon Cieslak — Partner. Law clerk to Judge Jeffrey T. Miller of the Southern District of California; nearly a decade at Cooley.
Luke Hasskamp — Partner. Argued and won Chase Manufacturing v. Johns Manville in the Tenth Circuit; three federal clerkships; part of the Bona Law team that served as outside litigation counsel to the California Attorney General in People v. Vitol.
Aaron Gott — Partner. Argued and won the Ariix v. NutriSearch and PharmacyChecker.com v. LegitScript appeals in the Ninth Circuit; part of the California AG Vitol team.
Luis Blanquez — Partner. Fifteen years of U.S. and European competition experience, including the European Commission's Merger Task Force; defended In re Capacitors (N.D. Cal.).
Joseph Trujillo — Partner. Stanford Law School; law clerk to Judge Phyllis Hamilton (N.D. Cal.); previously at Dechert and Orrick; litigates under California's Unfair Practices Act, Section 17200, and trade-secret statutes; leads the defense of the Santa Monica UCL enforcement action.
Kristen Harris — Of Counsel. Vice Chair of the ABA Antitrust Law Section's Trade, Sports, and Professional Associations Committee and former Counsel to the Section's Chair; previously practiced antitrust at Axinn; part of the Bona Law team that served as outside litigation counsel to the California Attorney General; U.S. Marine Corps veteran.
Steven Madoff — Of Counsel. Former Executive Vice President of Business & Legal Affairs at Paramount Pictures; media and entertainment antitrust counseling from decades inside California's signature industry.
Kimberly Straight-Gagnon — Discovery Counsel; formerly in-house discovery counsel at MGM; manages discovery across the firm's California litigation.

The full firm stands behind them: the broader Vitol trial team included partners resident in our Dallas and New York offices, and our merger, counseling, and appellate benches work on California matters wherever they sit.

What We Do

Cartwright Act and UCL litigation, both sides. We prosecute claims for businesses injured by price-fixing, group boycotts, and exclusionary conduct — with treble damages and attorneys' fees available — and we defend companies sued under the Cartwright Act, the UCL, and the UPA, including UCL and false-advertising actions brought by cities and public prosecutors. See our antitrust litigation practice and, for strong affirmative claims, our flexible and hybrid fee arrangements. If you are weighing a potential claim, start with our independent antitrust claim evaluation — a privileged, fixed-fee assessment of whether the claim is worth pursuing. Large purchasers deciding whether to stay in a class or pursue their own recovery should see our opt-out and direct-action practice.
Monopolization and single-firm conduct, both sides. We prosecute Sherman Act Section 2 claims for California businesses injured by dominant competitors, suppliers, and platforms, and we defend companies accused of monopolization or exclusionary conduct. With the COMPETE Act effective January 1, 2027, we also assess exposure for companies with a strong position in a California market — pricing and discount structures, exclusive dealing, distribution and platform-access rules, refusals to deal, and hiring restraints — through a privileged, fixed-fee market-power review. See our monopolization and exclusionary conduct practice and Paul Moore's analysis of the final law.
California antitrust class action defense. Cartwright Act indirect-purchaser classes raise distinct certification, choice-of-law, and pass-on issues that we have litigated and won. See antitrust class action defense. For companies new to this, start with our primer, Help! My Company Is a Defendant in an Antitrust Class Action.
California Attorney General and district attorney investigations and enforcement. When the AG's Antitrust Section or a county district attorney opens an investigation or serves a CID or subpoena, we defend it, informed by having prosecuted on the government's side. And when government itself is the anticompetitive actor — a city, a licensing board, an exclusive franchise — we challenge it: see our practice on antitrust challenges to government action. See also our State Attorney General antitrust practice and antitrust investigations practice; if you have received a third-party subpoena in a California case, start with our guide to challenging or quashing it.
SB 25 filings and California merger review. We prepare California premerger notifications alongside federal HSR filings, track the Attorney General's implementing guidance as it issues, and know the State's merger-review playbook: our team includes the partner who led California's successful challenge to the Valero/Plains All American transaction. See our mergers and acquisitions practice.
California counseling and compliance. Pricing, MAP, and distribution programs under California's per se RPM rule (see our distribution and pricing practice and our retail and consumer-products page); AB 325 algorithmic-pricing compliance; information exchanges and trade associations; non-compete and no-hire questions under § 16600; state licensing-board conduct after North Carolina Dental (and judicial review of board decisions); price-gouging exposure during declared emergencies. See antitrust counseling and compliance.
California appeals. We brief and argue antitrust and competition appeals in the Ninth Circuit and the California Courts of Appeal — see our appellate litigation practice, our Ninth Circuit practice guide, and our primer on California state appellate procedure.
Co-counsel for California firms. When a case develops a Cartwright Act or UCL dimension — or a deal suddenly needs a California filing — we serve as antitrust co-counsel to litigation and deal firms without antitrust benches.

Industry depth where California's economy lives. Our California matters track the State's signature industries: software and technology platforms, media, sports, and entertainment, healthcare and life sciences, agriculture and food, real estate and housing, energy and commodities trading, and retail and e-commerce. We advise private equity sponsors and their portfolio companies on California filings and portfolio exposure, and we regularly guide international companies whose first encounter with U.S. antitrust law is a California one.

California Antitrust Law Is Not Federal Antitrust Law

The Cartwright Act (Cal. Bus. & Prof. Code § 16700 et seq.) overlaps with the Sherman Act, but the differences are where California cases are won:

Indirect purchasers can recover. California repealed Illinois Brick by statute (§ 16750), so customers further down the distribution chain — and the classes they form — can seek treble damages that federal law denies them. Choosing which claims belong in which court — and whether a state-court case can be removed to federal court — is often the first strategic decision in a California antitrust dispute. Our attorneys have litigated exactly this boundary: in the Capacitors MDL we defeated indirect-purchaser class certification because California choice-of-law rules required applying each state's own law, defeating predominance.
Resale price maintenance is treated more harshly. Federal law reviews RPM under the rule of reason after Leegin; California authority continues to treat vertical price-fixing as per se unlawful, so national pricing programs must be designed against California, not the federal baseline. Our distribution, dealer termination, and pricing practice builds MAP and unilateral-pricing programs with exactly that constraint in mind, and our retail, e-commerce, and consumer-products team applies it for national brands and marketplace sellers — see our analyses of RPM under California law, the Colgate doctrine, and when a MAP policy violates the antitrust laws.
Algorithmic pricing is expressly regulated. AB 325 (effective January 1, 2026) amended the Cartwright Act to prohibit using or distributing a "common pricing algorithm" that draws on competitor data as part of an agreement to set or recommend prices or commercial terms — including wages — or coercing others to adopt its recommendations, and lowered the pleading bar for conspiracy claims: a California plaintiff no longer must plead facts excluding independent action. A broader ban on "surveillance pricing" (AB 2564) passed both houses but died on the session's last night without the Assembly concurrence vote it needed. We have covered the algorithmic-pricing litigation wave since it began.
The penalties went up. SB 763 (effective January 1, 2026) raised Cartwright Act criminal fines to $6 million per violation for corporations and $1 million for individuals, and authorized civil penalties of up to $1 million per violation in actions brought by the Attorney General or a district attorney.
Single-firm conduct — California now has its own monopolization law. The Cartwright Act has never reached unilateral monopolization, so plaintiffs have paired it with Sherman Act Section 2 claims in federal court. AB 1776, the COMPETE Act, signed September 30, 2026 and effective January 1, 2027, adds Sections 16730–16732 to the Business and Professions Code and makes it unlawful to monopolize or monopsonize any part of California trade or commerce, or to attempt, maintain, or conspire to do so — on proof of "substantial market power" by direct or indirect evidence, under California's own analytical framework rather than federal Section 2 doctrine, with competition for workers expressly protected and market power earned through superior products or business acumen expressly lawful. The final law is narrower than the bill as introduced: only the Attorney General and district attorneys may sue, there is no private right of action, private plaintiffs cannot use a violation as a UCL predicate, and independently owned California businesses with no more than 100 employees and $10 million in average annual gross receipts are exempt, as is conduct within a government-granted and supervised franchise, license, or permit. Private plaintiffs will still need Section 2 — see our roadmap for private monopolization plaintiffs after the Google decisions and our analysis of direct actions against Google after the Google Play settlement — while, from January 2027, any company with a strong position in a California market faces a public enforcer armed with a lower bar than federal law. Companies that have grown by acquisition should map the overlap between their deals and their California positions. Read Paul Moore's analysis of what the final law does and does not do; Bona Law's monopolization and exclusionary conduct practice works both sides of that line.
Beyond the Cartwright Act. The Unfair Practices Act (§ 17000 et seq.) reaches below-cost pricing, locality discrimination, and secret rebates that federal law leaves alone; the Unfair Competition Law (§ 17200) sweeps more broadly than any federal analogue and rides alongside almost every California competition case — and cities and public prosecutors are reaching for it too, as in the City of Santa Monica's novel use of the UCL against a property owner to enforce a local rental ordinance that we are defending. See our guide to defending a Section 17200 claim and our complex commercial litigation practice. And California's ban on certain non-compete agreements (§ 16600) — void regardless of where or when they were signed since 2024, though judged under a rule of reason in business-to-business contracts — generates competition disputes of its own: see our labor antitrust practice and our explainer on out-of-state non-competes in California.

The New Era of California Antitrust Enforcement

California is in the middle of the most consequential rewrite of its competition laws in decades, and its Attorney General is litigating at a pace few other states match. In the span of a year the Legislature has regulated pricing algorithms (AB 325), multiplied the Cartwright Act's penalties (SB 763), created a state premerger filing (SB 25), and enacted a monopolization statute (the COMPETE Act). The California Uniform Antitrust Premerger Notification Act (SB 25) requires many HSR filers to deliver a copy of their federal filing to the California Attorney General within one business day — for HSR filings on or after January 1, 2027, with penalties up to $25,000 per day. Our deal-team-ready compliance checklist walks through who is covered, the mechanics, and confidentiality; the Attorney General has not yet published its filing portal or regulations.

On the enforcement side, the Attorney General's Cartwright Act and UCL case against Amazon is set for trial in San Francisco Superior Court on March 22, 2027; California is leading a multistate Clayton Act challenge to the Paramount–Warner Bros. Discovery transaction, set for trial in March 2027; and on August 31, 2026, the office joined the FTC and a bipartisan coalition of other states in new UCL and false-advertising claims over Amazon's advertising auctions — all alongside continuing work on algorithmic rent-pricing, no-poach agreements, and healthcare consolidation. From January, that docket gains a monopolization statute. Bona Law tracks these developments as a participant, not a spectator: our partner Paul Moore publishes Inside State Enforcement, covering California competition and AG enforcement.

California Antitrust FAQs

What is the difference between the Cartwright Act and the Sherman Act? The Sherman Act is the federal antitrust statute; the Cartwright Act is California's. They overlap, but California is broader where it counts: indirect purchasers can recover treble damages, resale price maintenance is treated as per se unlawful, pricing algorithms are expressly regulated, and pleading a conspiracy is easier after AB 325. Until 2027 the Cartwright Act does not reach single-firm monopolization at all; the COMPETE Act adds a monopolization and monopsonization provision, enforceable by the Attorney General and district attorneys, effective January 1, 2027. Many California cases plead both statutes.

What is California's COMPETE Act, and does it apply to my company? AB 1776, signed September 30, 2026, adds a monopolization and monopsonization prohibition (Section 16731) to the Cartwright Act, enforceable from January 1, 2027 by the Attorney General and district attorneys against any business with "substantial market power" in a California market — a term the statute does not define. Independently owned California companies with no more than 100 employees and $10 million in average annual gross receipts are exempt, and market power earned through superior products, services, or business acumen remains lawful. A company with a meaningful share of a California product, service, or labor market should know how its markets would be defined and whether its pricing, distribution, access, and hiring practices could be characterized as exclusionary. Read Paul Moore's analysis of the final law.

Can a private plaintiff sue for monopolization under California law? Not under the Cartwright Act, even after the COMPETE Act: the Legislature removed the private right of action, limited enforcement to the Attorney General and district attorneys, and barred private plaintiffs from using a violation as a UCL predicate. Private monopolization claims arising in California are brought under Sherman Act Section 2, usually in federal court and often alongside Cartwright Act and UCL claims for related concerted conduct. Our monopolization practice handles both, and our independent antitrust claim evaluation is the place to start if you believe a dominant company has injured your business.

Can a district attorney or city attorney bring a competition case against my company? Yes. Local prosecutors enforce the Unfair Competition Law and False Advertising Law, district attorneys share Cartwright Act enforcement authority with the Attorney General, and from January 1, 2027 district attorneys can also bring monopolization and monopsonization actions under the COMPETE Act. Local enforcement is real and growing — our client in the Santa Monica UCL enforcement action is one example. A letter or subpoena from a district attorney or city attorney should be treated with the same seriousness as one from the Attorney General: preserve documents, map your exposure, and engage counsel before responding. See our State Attorney General antitrust practice and our guide to defending a Section 17200 claim.

Can indirect purchasers sue under California antitrust law? Yes. Unlike federal law, California lets indirect purchasers — businesses and consumers who bought through intermediaries — recover damages under § 16750. That is why nationwide price-fixing cases so often include Cartwright Act classes, and why certification and choice-of-law fights often decide them. Businesses with large purchase volumes should also weigh whether to opt out of the class and pursue their own claims — see our analysis of which software developers should consider a direct action against Google after the $700 million Google Play settlement approved in the Northern District of California.

Is resale price maintenance illegal in California? California treats vertical price-fixing more strictly than federal law. Setting the resale prices your dealers or retailers must charge carries real Cartwright Act and UCL risk even where federal law would apply the rule of reason. MAP programs need California-specific design — our distribution and pricing team does this work daily. Unilateral pricing policies remain available — see the Colgate doctrine and other alternatives to RPM.

Does California require its own merger filing? Starting with HSR filings made on or after January 1, 2027, yes — SB 25 requires covered filers to submit their HSR form to the California AG within one business day, with penalties up to $25,000 per day. It is mandatory but non-suspensory: it should not hold up your deal if handled correctly. Start with our compliance checklist, which we will update when the Attorney General publishes its filing procedures. Our merger team prepares the California and federal filings together, and for how the Attorney General's office reviews deals, see our best practices for merger reviews before the federal agencies and the California Attorney General.

The California Attorney General sent us a CID or subpoena. What should we do? Treat it like the start of litigation: preserve documents immediately, map your exposure before responding, and engage counsel who knows how the AG's Antitrust Section builds cases. Our team includes a former senior Deputy Attorney General from that section. See our antitrust investigations practice; if the subpoena reached you as a non-party, start with our guide to challenging or quashing a third-party subpoena in California.

Do you represent plaintiffs or defendants? Both. We defend companies in Cartwright Act class actions, AG investigations, and public-prosecutor enforcement actions; we prosecute claims for businesses injured by anticompetitive conduct; and we have served as outside trial counsel to the California Attorney General. For strong affirmative claims we consider hybrid and contingent fee structures, and we offer an independent, fixed-fee antitrust claim evaluation for companies deciding whether a claim is worth bringing.

California Antitrust Resources

Talk to a California Antitrust Lawyer
Bona Law is headquartered in San Diego and litigates California antitrust matters statewide — in the Superior Courts, every federal district in California, and the Ninth Circuit. Whether you are defending a Cartwright Act class action or AG investigation, weighing claims against a competitor, preparing an SB 25 filing, or building a California-compliant pricing program, contact Bona Law for an initial discussion: 858-964-4589 or info@bonalawpc.com. Companies deciding whether to pursue a claim can also request an independent antitrust claim evaluation.