Court clears path for private damages in Google ad tech cases

On October 27, 2025, the United States District Court for the Southern District of New York granted partial summary judgment to multiple private plaintiffs pursuing antitrust damages against Google LLC. Judge P. Kevin Castel ruled that findings from the Eastern District of Virginia establishing Google's monopolization of digital advertising markets would have binding effect in private litigation.

The 34-page opinion applies issue preclusion to several critical determinations made by Judge Leonie M. Brinkema in April 2025. According to the ruling, Google cannot relitigate its liability for monopolizing worldwide markets in publisher ad servers and ad exchanges. The court determined that Google's anticompetitive conduct, including unlawful tying of its DoubleClick for Publishers platform to its AdX exchange, has already been proven through a three-week bench trial in Virginia.

"Judge Brinkema's findings of fact and conclusions of law are precise and concise," according to Judge Castel's opinion. The Virginia court's 115-page decision following extensive testimony and evidence review was "far from tentative," providing Google with a "full and fair opportunity to litigate" the issues.

The ruling affects several categories of plaintiffs. Publisher movants including Associated Newspapers Ltd., Mail Media Inc., Gannett Co. Inc., and a putative class of publishers obtained preclusion on multiple findings. The court barred Google from relitigating the existence of separate markets for publisher ad servers and ad exchanges, both defined as worldwide in scope excluding countries with internet censorship or subject to United States sanctions.

Publishers can now proceed directly to proving damages based on established findings that Google maintained over 90 percent market share in publisher ad servers from 2018 to 2022. The Virginia court had found Google's DoubleClick for Publishers, acquired in 2008 for $3.1 billion, held at least 91 percent of the worldwide ad server market.

Multiple anticompetitive practices are now binding law in private cases. The court's ruling precludes Google from contesting that it engaged in unlawful tying, First Look policies giving AdX preferential access to inventory, Last Look advantages allowing Google to win auctions by minimal margins, Dynamic Revenue Share adjustments that deflated competing exchanges, and Unified Pricing Rules preventing publishers from charging Google higher rates than competitors.

The opinion addresses Google's arguments about Circuit differences in antitrust standards. Google had contended that Fourth Circuit standards applied by Judge Brinkema differed materially from Second Circuit law governing the New York litigation. Judge Castel rejected these claims as "utterly without merit."

On tying arrangements specifically, Google argued Second Circuit precedent requires explicit proof of anticompetitive effects in the tied market beyond Fourth Circuit requirements. The court found Judge Brinkema's decision satisfied even this stricter standard. The Virginia ruling documented how Google's tying of DoubleClick for Publishers to AdX enabled implementation of Unified Pricing Rules that "reduced their ability to control ad pricing, maintain ad quality and diversify their sources of revenue" for Google's largest publisher customers.

The court analyzed whether Google's refusal-to-deal defenses based on Verizon Communications Inc. v. Law Offices of Curtis V. Trinko applied to the conduct at issue. Judge Castel found Judge Brinkema correctly distinguished the Supreme Court precedent. The Virginia court had noted that Trinko addressed monopolist refusals to deal with competitors, not anticompetitive restraints placed on customers. Google's conduct involved tying arrangements and direct interference with publishers' ability to deal with rival exchanges.

Judge Castel addressed Google's argument about two-sided transaction platforms. Google contended the ad exchange constituted a single two-sided market under Ohio v. American Express Co., requiring analysis of both advertiser and publisher sides simultaneously. The court found Judge Brinkema appropriately considered Amex principles while recognizing critical differences. Ad exchanges function as auction houses evaluating multiple buyers and selecting highest bidders, not merely facilitating transactions between parties.

The ruling establishes finality for preclusion purposes despite ongoing remedies proceedings in Virginia. Judge Castel applied Second Circuit precedent from Lummus Co. v. Commonwealth Oil Refining Co., which permits preclusive effect for determinations that are "sufficiently firm" even without final judgment. The court noted three relevant factors: the Virginia decision was not tentative, the three-week trial provided adequate hearing, and appellate review remains available after remedies trial completion.

Google raised concerns about additional discovery developed in the multidistrict litigation that was unavailable during the Virginia trial. The court found this argument unpersuasive. Google demonstrated no evidence that later-developed materials would have been outcome-determinative on any claim. The ruling noted Rule 60(b) of the Federal Rules of Civil Procedure would provide Google remedy if the Virginia liability finding were reversed on appeal.

The opinion grants more limited relief to advertiser plaintiffs. Named plaintiff Cliffy Care Landscaping LLC faces arbitration proceedings, while Hanson Law Office's claims regarding Unified Pricing Rules post-date the statute of limitations for its alleged injury period. The court granted advertisers preclusion only on market definition for ad exchanges and Google's monopoly power in that market.

Inform Inc. obtained preclusion on ad server and ad exchange market definitions plus four specific anticompetitive practices. The former online video publisher, which alleges Google's conduct drove it from business, can now proceed to damages on established liability for Unlawful Tying, First Look, Last Look, and Dynamic Revenue Share.

The ruling emphasizes that preclusion does not relieve plaintiffs of proving antitrust injury and damages specific to their circumstances. According to Brunswick Corp. v. Pueblo Bowl-O-Mat, Inc., plaintiffs must still demonstrate harm flowing from the anticompetitive aspects of Google's conduct. Publisher expert reports concerning presence and activities in relevant markets remain necessary for damages calculations.

Judge Castel rejected fairness arguments against applying nonmutual offensive issue preclusion. The court found Google faced "massively high stakes" in defending the Department of Justice enforcement action while simultaneously litigating the multidistrict proceeding. The risk of collateral estoppel was apparent and foreseeable. Congress amended Section 5(a) of the Clayton Act in 1980 specifically to clarify that "nothing contained in this section shall be construed to impose any limitation on the application of collateral estoppel" from government antitrust actions.

The court distinguished its ruling from the AdSense Publishers Class claims. Judge Brinkema concluded that AdSense and AdWords components of Google's advertiser ad network did not constitute a proven relevant market in the Virginia proceedings. The New York court's preclusion analysis therefore excludes AdSense-related claims.

The procedural history traces back to August 10, 2021, when the Judicial Panel on Multidistrict Litigation consolidated federal actions against Google regarding digital advertising business. The multidistrict litigation included state attorneys general claims, publisher class actions, advertiser class actions, and individual actions. The court used the state attorneys general Third Amended Complaint as bellwether pleading for motion to dismiss proceedings.

The Department of Justice filed its Eastern District of Virginia action on January 24, 2023, approximately four months after Judge Castel ruled on the bellwether motion. Google unsuccessfully moved to transfer the Virginia case to the Southern District of New York for coordinated proceedings. The parties agreed to coordination orders allowing discovery sharing and non-duplicative witness questioning across both proceedings.

State attorneys general cases were remanded to the Eastern District of Texas on June 5, 2023, pursuant to the State Antitrust Enforcement Act of 2021. The federal law, signed December 29, 2022, required transfer of state antitrust actions. Private actions remained in the Southern District of New York multidistrict proceeding.

Fact and expert discovery completed in the New York actions as of December 2024. The court granted publisher movants leave to amend complaints to conform geographic market allegations with Judge Brinkema's worldwide market findings. Judge Castel noted Google's expert had addressed both United States and worldwide markets in the multidistrict litigation, preventing unfair prejudice from conforming amendments.

Class certification motions remain pending for both publisher and advertiser putative classes. Publishers seek certification of two classes: United States-based publishers who paid fees to Google or experienced revenue reductions for ad exchange services associated with AdX, and those associated with AdSense packages. Advertisers seek class certification for those who placed display advertisements on third-party websites using Google Ads during the relevant period.

The court granted partial summary judgment to publisher movants on five anticompetitive conduct findings plus the unlawful tying claim under Section 1 of the Sherman Act. Inform obtained similar relief excluding Unified Pricing Rules, which the company did not allege. Advertisers received preclusion only on ad exchange market definition and Google's monopoly power in that market.

Judge Castel's opinion addresses the "actually and necessarily determined" requirement for issue preclusion. The court noted that bench trial findings avoid difficulties inherent in jury verdicts. When multiple anticompetitive conduct patterns go to a jury without special verdict forms specifying which conduct was proven, subsequent courts cannot determine which findings have preclusive effect. Judge Brinkema's detailed findings eliminated this problem.

The Virginia court found that Google maintained its monopoly power "not by growth or development as a consequence of a superior product, business acumen or historic accident." Judge Brinkema determined procompetitive justifications for Google's anticompetitive conduct were "both invalid and insufficient" under the Microsoft framework. The judge found procompetitive benefits "far outweighed by anticompetitive effects."

Evidence in the Virginia trial included testimony from 39 live witnesses, excerpts from 20 deposition witnesses, and hundreds of exhibits. The testimonial phase lasted 15 trial days from September 9 through September 27, 2024. Judge Brinkema deferred closing arguments until November 25, 2024, providing parties time to review the extensive trial record.

Pre-suit investigation produced nearly three million documents from Google and nearly five million from third parties. The Department of Justice examined 30 witnesses before filing the complaint. During formal discovery, Google produced approximately 1,995,869 documents between September 8 and October 6, 2023, supplementing roughly three million pre-complaint documents and one million produced earlier in litigation. Ten Google witnesses and 20 third-party witnesses testified at depositions.

The ruling notes Google unsuccessfully argued Judge Brinkema employed a "monopoly broth" standard improperly aggregating conduct. The court found each of five practices—Unlawful Tying, First Look, Last Look, Dynamic Revenue Share, and Unified Pricing Rules—received independent scrutiny. Judge Brinkema did not find acquisitions of DoubleClick or Admeld anticompetitive despite their role establishing Google's position across the advertising technology stack.

The opinion distinguishes alternative findings from multiple anticompetitive findings. Neither side identified alternative grounds in Judge Brinkema's opinion. The Virginia court made no finding that any practice was lawful yet contributed to monopolization. Each anticompetitive act independently supported the monopolization conclusion.

According to the Virginia ruling, Google's First Look policy gave AdX initial opportunity to beat publisher-set floor prices. If AdX topped the minimum floor, the auction concluded without other exchanges receiving opportunity to submit competing bids. Publishers using DoubleClick for Publishers were required to offer AdX this preferential position in every auction.

Last Look allowed AdX to see competing exchanges' sealed bids before submitting final offers. Google implemented this feature to counter header bidding, which publishers developed as workaround to Google's auction advantages. Judge Brinkema characterized Last Look as anticompetitive conduct that "entrenched Google's monopoly power, disadvantaged Google's publisher customers, and harmed the competitive process."

Dynamic Revenue Share enabled Google to adjust percentage fees charged by AdX based on competitive pressure. The system lowered take rates on impressions receiving relatively high offers from third-party exchanges through header bidding. Google designed the feature to prevent publishers from recognizing better monetization opportunities with competing exchanges.

Unified Pricing Rules, implemented around 2019, prohibited publishers using DoubleClick for Publishers from setting higher price floors for AdX than for competing exchanges. Publishers viewed the restriction as contrary to their interests but "felt stuck using DFP given its tie to AdX," according to the Virginia findings. The policy reduced publisher ability to introduce competition through differential pricing.

The court rejected Google's argument that Second Circuit law requires dismissal of monopolization claims unless conduct lacks any legitimate business purpose. Judge Castel noted the Microsoft framework for balancing procompetitive and anticompetitive effects applies in both circuits. The Southern District of New York's motion to dismiss ruling requiring conduct "without a legitimate business purpose" did not foreclose later analysis of whether slight procompetitive benefits outweigh substantial anticompetitive harms.

The opinion emphasizes Congress explicitly authorized issue preclusion from government enforcement actions through 1980 amendments to the Clayton Act. The Antitrust Procedural Improvements Act added language clarifying that "nothing contained in this section shall be construed to impose any limitation on the application of collateral estoppel." This legislative history demonstrates congressional intent to facilitate private follow-on litigation after successful government prosecutions.

Issue preclusion from bench trials to jury trials poses no Seventh Amendment concerns under Parklane Hosiery Co. v. Shore. The Supreme Court held in 1979 that prior bench trial findings may have preclusive effect in subsequent jury trials. Google's entitlement to jury trial in private actions does not prevent application of established liability findings from the Virginia bench trial.

Judge Castel noted the ruling promotes efficiency and avoids jury confusion. Forcing juries to reconsider identical liability issues already determined through three-week trial and 115-page opinion would waste judicial resources. The findings come from recent proceedings, issuing just seven months before the summary judgment motions, with no material changes in controlling legal principles.

The court found no special circumstances warranting exception to normal preclusion rules. Montana v. United States requires consideration of whether controlling facts or legal principles changed significantly and whether other circumstances suggest unfairness. The short time interval and absence of inconsistent prior Google victories support application of collateral estoppel.

Google's argument about being deprived of later-developed discovery in the multidistrict litigation failed to establish unfairness. The company neither demonstrated materiality of additional evidence nor sought relief from Virginia findings based on newly-discovered evidence. Moving plaintiff expert reports concerning their specific circumstances and damages calculations fall outside preclusion scope, which addresses only liability elements.

The ruling terminates motions at multiple docket numbers across the consolidated cases. Separate motions to provisionally seal submissions received approval, allowing redacted versions to appear on public dockets. The court directed the clerk to terminate specific motions across six separate case numbers within the multidistrict litigation.

Private plaintiffs can now proceed directly to damages phases with established liability. Publishers must prove antitrust injury stemming from the specific anticompetitive practices plus causation and quantification of harm. Expert economic testimony will address what auction clearing prices would have been absent Google's conduct. Advertisers face similar burdens demonstrating financial harm flowing from proven monopolization.

The ruling adds to mounting legal pressure on Google's advertising technology business. Combined with the April 2025 liability finding and ongoing remedies proceedings, the company faces potential structural remedies including forced divestiture of ad tech assets. The Department of Justice and state plaintiffs have proposed breaking up Google's integrated advertising platform.

Timeline

• 2008: Google acquires DoubleClick for $3.1 billion, obtaining dominant publisher ad server and nascent ad exchange
• 2011: Google acquires Admeld, a yield management tool helping publishers optimize ad network decisions
• 2014-2015: Header bidding emerges as publishers seek to mitigate Google's advantages in the ad tech stack
• 2017: Google implements Project Poirot to adjust bids benefiting AdX over rival exchanges
• 2019: Google implements Unified Pricing Rules restricting publishers' ability to set higher price floors for AdX
• August 10, 2021: Judicial Panel on Multidistrict Litigation transfers federal actions against Google to Southern District of New York
• September 13, 2022: Judge Castel grants in part and denies in part motion to dismiss state attorneys general bellwether complaint
• January 24, 2023: United States Department of Justice and eight states file Eastern District of Virginia antitrust action
• April 2023: Nine additional states join Virginia lawsuit
• June 5, 2023: Judicial Panel remands state attorneys general actions to Eastern District of Texas
• September 9-27, 2024: Three-week bench trial in Eastern District of Virginia on liability issues
• November 25, 2024: Closing arguments in Virginia trial
• April 17, 2025: Judge Brinkema issues 115-page ruling finding Google liable for monopolization and unlawful tying
• May 5, 2025: Parties submit competing remedy proposals in Virginia case
• August 4, 2025: OpenX Technologies files follow-on antitrust lawsuit seeking damages
• August 29, 2025: Dotdash Meredith files comprehensive antitrust complaint in Southern District of New York
• September 8, 2025: PubMatic files antitrust lawsuit in Eastern District of Virginia
• September 22, 2025: Remedies trial begins in Eastern District of Virginia
• October 2, 2025: Law firms begin recruiting advertisers for potential damages claims
• October 27, 2025: Judge Castel grants partial summary judgment in Southern District of New York multidistrict litigation

Summary

Who: Judge P. Kevin Castel of the United States District Court for the Southern District of New York ruled in favor of multiple private plaintiffs including Associated Newspapers Ltd., Mail Media Inc., Gannett Co. Inc., a putative class of publishers, Inform Inc., and putative advertiser class representatives against Google LLC.

What: The court granted partial summary judgment applying issue preclusion from Judge Leonie M. Brinkema's April 17, 2025 Eastern District of Virginia ruling. Google cannot relitigate liability for monopolizing worldwide publisher ad server and ad exchange markets or for unlawfully tying DoubleClick for Publishers to AdX. The ruling binds Google to findings that it engaged in five specific anticompetitive practices: Unlawful Tying, First Look, Last Look, Dynamic Revenue Share, and Unified Pricing Rules.

When: Judge Castel issued the 34-page opinion on October 27, 2025, seven months after Judge Brinkema's liability ruling and approximately four years after the Judicial Panel on Multidistrict Litigation consolidated private antitrust actions against Google in August 2021.

Where: The ruling applies to the multidistrict litigation consolidated in the United States District Court for the Southern District of New York. The preclusive findings originated from three-week bench trial in the United States District Court for the Eastern District of Virginia. The relevant markets are worldwide in scope, excluding countries with government internet censorship or subject to United States economic sanctions.

Why: The ruling matters because it accelerates private damages litigation by eliminating need to reprove liability established through extensive government prosecution. Publishers, advertisers, and ad tech companies can proceed directly to calculating financial harm from Google's proven monopolization. The decision affects hundreds of millions or billions of dollars in potential damages claims while demonstrating federal courts' willingness to apply issue preclusion from government antitrust victories. Combined with ongoing Virginia remedies proceedings potentially forcing structural changes to Google's ad tech business, the ruling intensifies pressure on the company's core advertising revenue model that funded its dominance across multiple technology sectors.