The U.S. Department of Justice is asking a federal court to force Google to divest critical pieces of its ad-technology stack—namely its AdX ad exchange and DFP ad server (part of Google Ad Manager)—after Judge Leonie Brinkema last year found Google to have unlawfully monopolized those markets. In the remedies phase, the DOJ argues that merely imposing behavioral constraints won’t be enough, and that a structural breakup is essential to prevent Google from reasserting dominance. Google counters that the DOJ’s proposals are overreaching, impractical, and could destabilize the ad ecosystem. A key moment in the trial came when Brinkema asked whether she could trust Google to comply in “complete good faith” under lighter remedies—a pointed question given past allegations that Google’s employees attempted to hide evidence in previous proceedings. A former Google engineer testified that migrating AdX and DFP is technically feasible within two years. The court is now deciding whether to accept Google’s behavioral fixes or enforce a structural separation.
Sources: Reuters, Financial Times
Key Takeaways
– The DOJ is pushing for a full structural remedy—a breakup of Google’s ad exchange (AdX) and publisher ad server (DFP)—arguing that behavioral solutions won’t prevent re-monopolization.
– Judge Brinkema is signaling skepticism: her question about trusting Google to act “in complete good faith” underscores doubt over compliance if lighter rules are imposed.
– Google disputes the feasibility and prudence of divestiture, warning of disruption to publishers and the ad ecosystem, though a former engineer countered these claims by testifying that a migration in two years is possible.
In-Depth
In April 2025, Judge Leonie Brinkema ruled that Google had unlawfully monopolized two core ad-technology markets: the ad exchange (AdX) and the publisher ad server (DFP). With that liability phase behind them, the courtroom has now moved into its most consequential chapter: what remedy, if any, should be imposed to break Google’s entrenched control and restore competition. The DOJ is making the argument that the only way to ensure lasting change is a structural break—forcing Google to divest or spin off its ad exchange and portions of its ad server machinery—rather than relying on behavioral restrictions alone.
Google’s counterargument hinges on several points. First, they contend that divestiture is technically risky and that migrating complex infrastructure could be impractical or harmful to publishers and advertisers. Second, they argue the DOJ’s proposals exceed what’s legally justified by the liability decision, pointing out that simpler behavioral remedies—like open bidding, rules on data sharing, or escrow mechanisms—might suffice without the disruption of a forced break up. Google further warns that dismantling integrated ad tools could undermine the monetization capabilities of small publishers dependent on its systems.
The trial’s dynamic introduces a critical tension: how much should the court rely on faith in Google’s compliance? In one memorable moment, Judge Brinkema asked whether any judicial order could succeed if one doesn’t trust Google to abide by it in “complete good faith.” That question carries weight given past allegations that Google employees attempted to obscure internal messages or communications tied to the previous liability phase. Given that history, Brinkema may lean toward remedies in which Google’s maneuvering room is limited by design.
Still, the DOJ has bolstered its structural remedy argument with technical testimony. A former Google engineer testified that migrating AdX and DFP is feasible within a two-year timeframe, undermining claims that divestiture is impossible. DOJ proponents have also proposed a phased approach—first making Google turn over “auction logic” to a third party or open-source repository, and then effecting a full spin-off.
Meanwhile, publishers watch nervously. They rely heavily on Google’s tools to monetize content. The DOJ has floated escrow proposals (such as depositing 50 percent of Google’s net revenues from affected ad units during transition) to cushion publishers from disruption, but many details remain unresolved. Observers also note that the broader ad ecosystem is already shifting—walled gardens, retail media platforms, and AI-driven ad models are reducing the centrality of open-web display advertising. That trend could mute the perceived impact of any remedy.
Whichever way the court rules, this decision may become a test case: will U.S. courts be willing to impose structural remedies on a major tech company, or will antitrust enforcement continue to favor behavioral constraints? The balance struck here could influence how aggressively regulators pursue Big Tech firms in the years ahead.