Quinn Emanuel Secures Historic Class Certification Victory for 200+ Million Consumers in Landmark Antitrust Case Against Amazon

In DeCoster v. Amazon, Quinn Emanuel and its co-counsel, Hagens Berman and Keller Postman, just secured a historic class certification victory for over 200 million American consumers —likely one of the largest classes ever certified in United States history in a landmark antitrust case against Amazon. This case is one of a coordinated set of actions against Amazon for anticompetitive conduct regarding the Amazon Marketplace, including actions by the Federal Trade Commission, the State of California, and the District of Columbia. After Quinn Emanuel defeated Amazon's aggressive legal challenges, including two motions to dismiss and 700+ pages of opposition to the Firm’s motion for class certification, Judge Chun granted Quinn Emanuel’s motion on August 6, 2025 (released publicly on September 2, 2025), in a detailed fifty-page order that validates the Firm’s comprehensive legal strategy.

The Firm’s case centers on Amazon’s anti-discounting policies that apply to selling on the Amazon Marketplace. Quinn Emanuel alleges that Amazon prevents businesses who sell on Amazon from selling their goods at lower prices anywhere else online, which makes it impossible for rival online marketplaces to challenge Amazon’s dominance by facilitating sellers’ ability to charge lower prices. At the same time, Amazon charges very high fees to all sellers, including a “referral” fee that applies to every single sale.  Without Amazon’s conduct, other marketplaces would charge lower fees, allowing sellers to charge lower prices, and Amazon would have to compete by lowering its own fees, driving price competition that would have widespread benefits.  But Amazon systematically prevents this from happening.  When anyone attempts to compete with Amazon on price by offering better deals on competing platforms like Temu or direct-to-consumer websites, Amazon punishes the relevant third-party sellers on Amazon’s marketplace by removing their products from the critical “Buy Box”, suspending shipping options, or terminating selling privileges entirely. Internal Amazon documents presented in the class certification briefing reveal the company’s own employees acknowledged this conduct “encourages sellers to raise their prices on competitor websites” and could be perceived as “price fixing.”

This conduct harms all or virtually all consumers. Because Amazon’s conduct blocks or inhibits price competition on platform seller fees (known as “referral fees”), every transaction on Amazon involves the payment of inflated referral fees that would have been lower in a world where marketplace platforms could compete on price. Quinn Emanuel demonstrated this class-wide impact through the economic analysis of the Firm’s economic expert Dr. Parag Pathak, a Professor of Economics at MIT.   

Quinn Emanuel’s victory represents a turning point against Amazon’s monopolistic practices. The Firm successfully demonstrated that Amazon's anti-discounting policy exists, impacts virtually all consumers, and constitutes clear anticompetitive conduct. In the process, the Firm also exposed Amazon’s practice of “privilege cloaking”—improperly marking ordinary business documents as privileged to hide evidence of anticompetitive intent. And despite Amazon dumping terabytes of previously undisclosed data in a last-ditch effort to delay proceedings during the class certification briefing stage, Quinn Emanuel demonstrated to the Court that our proffered expert economic analysis passed the rigorous standards courts apply to antitrust class certification motions.

Although Amazon now seeks interlocutory review, we believe their arguments lack merit. This landmark certification decision marks the beginning of accountability for Amazon’s systematic monopolization that has inflated prices for hundreds of millions of American consumers, and Quinn Emanuel looks forward to continuing to represent this class in the litigation.

This victory is the result of remarkable coordination among three firms.  During class certification, Quinn Emanuel took the lead on the economic issues, including a deposition of Amazon’s economic expert that showed his work had significant flaws.  Hagens Berman took the lead on briefing, and on the class certification argument.  And Keller Postman took the lead on exposing Amazon’s privilege cloaking activities, played a crucial role in briefing, and is now taking a leading role in defending this victory from any appeal.