Google Ad Tech Breakup Watch: Judge Brinkema’s Remedies Decision and What Divestiture Could Look Like

What the Liability Ruling Established

On 17 April 2025, US District Judge Leonie M. Brinkema of the Eastern District of Virginia ruled that Google illegally monopolized two distinct ad-tech markets: the open-web display publisher ad server market (where Google’s product is DoubleClick for Publishers, or DFP, also branded Google Ad Manager on the publisher side) and the open-web display ad exchange market (where Google’s product is AdX). She also found Google liable for unlawfully tying DFP and AdX together — using publisher dependence on DFP to lock them into AdX, and using advertiser demand on AdX to lock publishers into DFP.

According to Simpson Thacher’s analysis, the case was brought by the Department of Justice and 17 states, and the EDVA decision is one of the few US monopolization rulings to find tying as an independent violation. The ruling is significant beyond the parties: it gave the DOJ a clean legal basis to seek structural remedies — not just behavioral fixes.

A separate case in the District of Columbia (the search distribution case under Judge Mehta) also went against Google in 2024 and produced its own remedies process. The two cases are distinct, but coverage often runs them together. The Brinkema case is specifically about the publisher-side ad-tech stack — the plumbing between websites and advertisers on the open web, not search.

Where the Remedies Trial Landed

The remedies phase ran in the second half of 2025, with closing arguments concluding on 21 November 2025, according to AdExchanger’s reporting. Judge Brinkema indicated during closing arguments that her team had begun drafting the decision and that she expected to release it “maybe next year” — meaning 2026. Pre-trial scheduling commentary suggested an early-2026 timing target.

Two competing remedy frameworks are now in front of the court.

The DOJ’s proposal is structural. It calls for the divestiture of AdX in full, and the open-sourcing of DFP’s “final auction logic” — the code that decides which bid wins the auction at the end of the chain. The DOJ’s reasoning, captured in coverage by Norton Rose Fulbright, is that behavioral remedies have a poor track record in fast-moving tech markets — Google has economic incentives to undermine any conduct rule, and a court cannot supervise the auction code in real time. The DOJ also reserved the right to seek divestiture of DFP itself “if necessary.”

Google’s proposal is behavioral. It would make real-time bids from AdX available to third-party ad servers (effectively unbundling AdX from DFP without divesting either), enjoin the contested auction-rule changes (Unified Pricing Rules, First Look, Last Look), share data files with publishers on request, and create a server-to-server integration between DFP and Prebid (the open-source header bidding wrapper used by many publishers as a competitive alternative). Google’s argument is that divestiture is technically and operationally impossible because DFP and AdX share infrastructure, customer data, and a single sales motion — and that behavioral remedies achieve the same competitive opening at a fraction of the implementation risk.

The Three Big Open Questions for the Decision

The Brinkema ruling will turn on three questions where the briefs disagree most sharply.

First, is structural divestiture of AdX feasible as a stand-alone product, given that AdX shares technical infrastructure with the rest of Google Ad Manager? The DOJ insists yes; Google says it would require years of disentanglement and would degrade service. Brinkema has signaled skepticism toward “ad tech window dressing” — meaning she is not satisfied with cosmetic separation that leaves Google’s structural advantages intact.

Second, does open-sourcing DFP’s auction logic actually restore competition, or does it simply hand competitors a code drop without the data and scale that make DFP work? Google’s economists argue that auction code without auction context is worthless. The DOJ argues that publishers and rivals can build comparable infrastructure once they can audit the rules of the game.

Third, what is the timing? Brinkema has flagged concern that structural remedies move slowly compared to behavioral ones, especially under appeal. If Google appeals a divestiture order, the structural remedy could be tied up in courts for years while the behavioral remedies — which are easier to defend on appeal — would already be in effect.

What This Means for Publishers, Advertisers, and the Open Web

Whatever Brinkema decides, the open-web advertising stack of 2026 will not look like the stack of 2024. Publishers, advertisers, and ad-tech rivals all need to translate the remedy options into concrete operational moves.

1. Publishers should rebuild the auction stack assuming AdX is no longer a default

Even a behavioral remedy will require Google to open AdX bids to third-party ad servers. That makes a header-bidding-first or hybrid Prebid + ad-server architecture the realistic 2026 default for any publisher with meaningful open-web revenue. The work to plan now: contract review with the current ad server, evaluation of independent ad servers (Kevel, Equativ, OpenX), and a pilot with Prebid’s server-side adapter. Publishers that still depend on DFP-AdX as a single default path are accepting the risk that the remedy resets their stack on someone else’s timetable.

2. Advertisers and their DSPs need a buy-side contingency plan

If AdX is divested or its auction logic is opened, the inventory composition of the open web shifts. Advertisers should ask their DSPs (DV360, The Trade Desk, Yahoo) for written commentary on how access to AdX inventory will change under each remedy scenario, and what the bidding-cost implications are. Major brands with annual programmatic budgets above $10M should run the same exercise with their primary ad-tech partner — not because Google itself disappears as an advertiser-side tool, but because the auction dynamics on the publisher side will reshape clearing prices.

3. Ad-tech rivals should plan around two scenarios — divestiture and structural-light

Independent ad-tech firms — exchanges, SSPs, ad servers, header bidding wrappers — should be running two parallel product roadmaps. Scenario A (full or partial AdX divestiture) creates a once-in-a-decade opening to win publisher market share; the product investment goes into onboarding, demand integration, and platform reliability. Scenario B (behavioral remedies only) creates a more incremental opportunity that hinges on transparency and auction-rule fairness. Building both roadmaps in parallel, rather than betting on one, is the prudent play because Brinkema’s ruling could split the baby in either direction.

4. Compliance and policy teams should follow the appeals path, not just the ruling

Whatever Brinkema decides, an appeal to the Fourth Circuit and possibly the Supreme Court is highly likely. Compliance and antitrust teams inside large advertisers, publishers, and ad-tech firms should set up a tracking process for: the appeal filing date, any stay-pending-appeal motions, the Fourth Circuit’s procedural calendar, and parallel remedies activity in the EU’s pending ad-tech investigation. The EU Commission’s own ad-tech case against Google is on a separate track but will be informed by the EDVA outcome — meaning a single ruling can shape global ad-tech regulation for the next decade.

The Antitrust Question

The Brinkema decision is more than a remedy in a single case. It is a precedent test for how aggressively US courts will use structural remedies in modern tech markets. The last comparable structural remedy was the 2001 settlement in US v. Microsoft — a case that ended in a behavioral order, not a breakup, and that shaped two decades of antitrust doctrine. Many critics argue the Microsoft outcome was too lenient and allowed dominance to persist; many defenders argue it preserved a working software market while disciplining specific conduct.

Brinkema is now writing the next chapter. If she orders structural divestiture of AdX, she signals that 21st-century antitrust enforcement is willing to break up integrated tech stacks — which has implications for every dominant platform with adjacent business lines, from Apple’s services bundle to Amazon’s marketplace-and-AWS combination. If she opts for behavioral remedies, she preserves the Microsoft template and shifts the burden back to legislators and regulators — meaning the EU, the UK CMA, and individual US states become the more aggressive enforcement venues by default.

For the open web, the stakes are concrete. Publishers have lost share to walled gardens (Meta, TikTok, Amazon, Google’s own owned-and-operated properties) for a decade. A meaningful Brinkema remedy is one of the few interventions that could restructure the economics in publishers’ favor. A weak remedy seals the existing trajectory.

Frequently Asked Questions

Sources & Further Reading

• District Court Rules Google Is a Monopolist in Ad Tech — Simpson Thacher
• Closing Arguments Are Done In The US v. Google Ad Tech Case — AdExchanger
• What you need to know from closing arguments in US v. Google — Norton Rose Fulbright
• Judge finds Google holds illegal online ad tech monopolies — CNBC
• DOJ v. Google: The DOJ And Google Sharpen Their Remedy Proposals — AdExchanger