Ad Tech Monopoly: Judge Rules Google Can't Relitigate Core Antitrust Facts

A judge has ruled, giving Google a blow in its ad tech monopoly legal battle. This ruling should help the plaintiffs suing Google not get hung up in court as long as some expected, plus Google can't relitgate the core facts in that antitrust case. This is seperate from the soft ruling of the first part of the Google monopoly ruling.

The court documents are over here and it says:

Moving Plaintiffs assert that Google is foreclosed from relitigating substantially identical issues that were actually and necessarily decided in the E.D. Va. Action under principles of issue preclusion, also known as collateral estoppel. Google opposes these motions on various grounds. For reasons that will be explained, the motions will be granted to the extent indicated and otherwise denied.

This seems to mean, I am no lawyer, that the core issue is whether a prior victory the U.S. government won against Google in a Virginia court (the E.D. Va. Action) can be used as a shortcut by all the other private companies and individuals suing Google in New York. The judge essentially said "Yes, for many of the key facts, Google already lost, so it can't argue them again." This is called "issue preclusion" or collateral estoppel.

The judge ruled that Google must accept the following facts as true in the New York cases, because they were already proven in the Virginia trial:

(1) The Market is Defined:

• The Products: There are two distinct markets in the ad world: publisher ad servers (software publishers use to manage ad space) and ad exchanges (the auction houses where buyers bid on the ad space).
• The Scope: These markets are worldwide (excluding countries like China or Iran with restricted internet access).

(2) Google's Actions Were Illegal:

The judge agreed that Google must accept the finding that it engaged in actions that were designed to protect and maintain its dominant position, which violates antitrust law. These actions include:

• Unlawful Tying: Forcing publishers to use Google's ad server (DoubleClick for Publishers or DFP) if they wanted to use Google's ad exchange (AdX). This is illegal under Section 1 of the Sherman Act.
• Specific Anti-Competitive Practices: Google is legally bound by the finding that the following four practices were illegal ways to protect its monopoly: (A) First Look, (B) Last Look, (C) Dynamic Revenue Share and (D) Unified Pricing Rules.

The plaintiffs still have to prove two things:

(1) Antitrust Injury: That Google's illegal actions specifically harmed them.

(2) Damages: How much money Google's actions cost them

Here is Jason's Kint summary of this, which is way better than I posted above:

Judge Castel: “Judge Brinkema’s findings of fact and conclusions of law are precise and concise.”
Her three-week trial & 115-page opinion are “far from tentative,” and Google had a “full and fair opportunity to litigate.” Google cannot reargue liability. /2 pic.twitter.com/FzE3UqOQF8

— Jason Kint (@jason_kint) October 28, 2025

Importantly, Judge Castel fully adopted Brinkema’s worldwide market definition for ad servers & ad exchanges. Google’s dominance - over 90% share in ad serving - is legally established for all of these other privacy cases. And European Commission should note this, too. /4

— Jason Kint (@jason_kint) October 28, 2025

Bottom line:
- DOJ’s win in EDVA is now the foundation for private damages cases.
- Google is barred from relitigating liability.
- As previously noted, “a precise and concise” opinion by Judge Brinkema now echoes through the Southern District of New York. BAM! /6

— Jason Kint (@jason_kint) October 28, 2025

And EDTX has now been alerted, too, for the State of Texas ++ case against Google which has significantly more additional claims, including deceptive action (and Jedi Blue) in it than DOJ had in EDVA... /8 pic.twitter.com/dELwnUR7T3

— Jason Kint (@jason_kint) October 28, 2025

Forum discussion at X.