Competitor False-Advertising Disputes — Prosecution and Defense — and Government Enforcement Defense
False advertising is a competition problem. The Lanham Act is one of the most powerful tools a business has to stop a rival from lying its way to market share. And, increasingly, businesses also need counsel when a government agency turns false-advertising laws against them.
When a competitor makes false or misleading claims about its products — or about yours — the damage shows up in lost sales, eroded margins, and a distorted market. Section 43(a) of the Lanham Act, 15 U.S.C. § 1125(a), offers businesses a federal cause of action to do something about it. And under state statutes like California's Unfair Competition Law (Cal. Bus. & Prof. Code § 17200) and False Advertising Law (§ 17500), cities, district attorneys, and attorneys general are bringing their own “false advertising” enforcement actions against legitimate businesses. Bona Law handles all three kinds of disputes: representing plaintiffs stopping a rival's deceptive campaign, defendants facing overreaching false-advertising claims, and businesses defending against government enforcement.
Featured: A Precedential Appellate Win in the Ninth Circuit
Ariix, LLC v. NutriSearch Corp. We represented a nutritional-supplement company alleging that a purportedly independent product-ratings guide had secretly rigged its ratings to favor a commercial partner in exchange for years of payments. The U.S. Court of Appeals for the Ninth Circuit issued a published decision reversing the dismissal of our client's Lanham Act false-advertising claim and clarifying when supposedly “independent” ratings cross the line into actionable commercial speech. Read the Ninth Circuit's opinion and our announcement of the decision.
Recent Developments
Competitor false-advertising litigation is growing — and so is government enforcement. Advertising-challenge filings before the National Advertising Division rose again in 2025, with health products and cosmetics among the most-challenged categories, and AI-generated claims and influencer marketing are opening new fronts. The law remains unsettled in ways that reward experienced counsel: the Supreme Court recently declined to resolve a circuit split over whether false “patented” or “proprietary” claims are actionable, so the answer depends on where the case is brought, and federal courts of appeals continue to sharpen the evidence a plaintiff needs to prove that consumers were actually misled. Meanwhile, California municipalities are testing aggressive new applications of the state's false-advertising laws against ordinary businesses — we are defending one of the first such cases now.
What We Handle
- Lanham Act § 43(a) false advertising — literally false and misleading claims about a competitor's or your own products.
- Comparative and superiority advertising — “#1,” “clinically proven,” “patented,” “made in the USA,” and similar claims.
- Rigged reviews and “independent” ratings — paid, disguised, or manipulated endorsements, ratings guides, influencer campaigns, and AI-generated claims.
- Industry “blacklists” and not-recommended lists — false or misleading warnings, safety designations, and de facto standards by associations and gatekeepers that steer customers away from a business.
- Government false-advertising enforcement defense — California UCL (§ 17200) and FAL (§ 17500) actions and similar other state laws brought by cities, district attorneys, and attorneys general.
- State unfair-competition and false-advertising law — California's UCL and FAL and their equivalents nationwide, on both the plaintiff and defense side.
- Companion competitor claims — trademark, trade-secret, tortious-interference, and unfair-competition counts that travel with false-advertising disputes.
- Appeals — we have taken false-advertising issues to the U.S. Courts of Appeals and won published decisions.
How We Help
Whether you are stopping a competitor's deceptive campaign, defending against an overreaching claim, or facing a government enforcement action, we focus on the questions that decide these cases: Is the statement actually false, merely misleading, or just puffery? Is it commercial advertising? What consumer and market evidence will the case require and when should it be developed? Can causation and competitive injury be proven? And what is the most efficient path to the result you need: A demand letter and negotiations? A federal complaint? Injunctive relief?
Representative Experience
Specific engagements are often confidential; the descriptions below convey the types of matters we handle.
- Secured a published Ninth Circuit reversal in a Lanham Act false-advertising case involving rigged “independent” product ratings (Ariix v. NutriSearch).
- Prosecuted Lanham Act false-advertising and Sherman Act monopolization claims against Johns Manville for falsely telling customers that our client's competing calsil insulation contained asbestos; after the false-advertising claim survived a motion to dismiss, we voluntarily dismissed it to focus the case on the antitrust claims, which produced a published Tenth Circuit reversal on summary judgment and, ultimately, a successful a jury verdict (Thermal Pipe Shields v. Johns Manville, D. Colo.).
- Defeated Lanham Act and RICO counterclaims for an online-pharmacy verification and price-comparison company, obtaining dismissal on proximate-cause grounds (PharmacyChecker.com v. LegitScript, D. Or. 2026).
- Defending a Southern California property owner against a novel city enforcement action under California's Unfair Competition Law and False Advertising Law, challenging both the underlying ordinance and the government's deception theories (People v. Enayati, L.A. Super. Ct.).
- Defended a retailer against Lanham Act and related claims arising from the alleged resale of branded products across multiple federal forums.
- Representing an online pharmacy-verification and price-comparison company prosecuting a Lanham Act false-advertising claim against a national pharmacy-boards association over “not recommended” and “unsafe” designations steering consumers away from its website (PharmacyChecker.com v. NABP, S.D.N.Y.; summary judgment pending).
- Won dismissal of the association’s Lanham Act and state and local consumer-protection counterclaims in the same action, on the ground that the association did not compete with our client and could not show injury to a commercial interest in sales or reputation, as Lexmark requires. Read our announcement of the decision.
- Counseled a consumer-products manufacturer on potential false-advertising, unfair-competition, and trademark claims against a former distributor, including pricing-misrepresentation and brand-harm issues.
- Represented competing businesses in trade-secret and unfair-competition disputes involving misappropriated customer, pricing, and technical information, and secured an arbitration award defeating a rival's most significant claims in a competitive-conduct dispute.
Featured Analysis
- Do I Have a Lanham Act Claim Against My Competitor for False Advertising? (Legal Resource)
- What is a Lanham Act False Advertising Claim and Why Does it Matter for Competition? (The Antitrust Attorney Blog)
- Defenses to a Section 17200 Unfair Competition Law Claim in California (Legal Resource)
- The Lanham Act and POM Wonderful LLC v. Coca-Cola: A Cause of Action for Competitors (The Antitrust Attorney Blog)
- Affirmative Defenses to Trademark Infringement Claims (Legal Resource)
Facing a competitor's false advertising, a false-advertising claim against you, or a government enforcement action?