Google and the Department of Justice present their closing arguments in the antitrust case concerning its advertising technology practices.

Google and the Department of Justice (DOJ) concluded their closing arguments in a critical antitrust case over Google’s online advertising dominance in a Virginia courtroom. Judge Leonie Brinkema, presiding over the case, is expected to issue a decision by the end of 2024. If she rules that Google’s ad tech system constitutes a monopoly, a second trial will determine potential remedies. A similar process is underway in a separate case concerning Google’s search practices.

During the three-hour session, both sides reiterated key points. The DOJ alleges that Google leveraged its ad tech products—especially DoubleClick for Publishers (DFP) and the AdX exchange—to unfairly dominate the market, pressuring advertisers and publishers. Google, however, maintains that it faces significant competition and shouldn’t be forced to collaborate with rivals. Judge Brinkema, having gained a solid grasp of the complex technical issues, challenged both sides’ arguments.

The Debate Over Market Definitions

A central issue is how to define the market in which Google operates. The DOJ identifies three distinct markets where Google allegedly holds dominance: publisher ad servers, ad exchanges, and advertiser ad networks. In contrast, Google argues that these are part of a single, two-sided market involving digital ad buyers and sellers, where it competes with platforms like Meta and TikTok.

Google cited the 2018 Supreme Court case Ohio v. American Express to support its argument. That case treated credit card merchants and users as part of a single market and required proof of harm on both sides, setting a high bar for antitrust claims. Judge Brinkema, however, expressed skepticism about applying this precedent to the Google case. While she initially found the analogy compelling, further analysis led her to believe the situations are significantly different.

She also questioned why the DOJ’s case focused primarily on publishers rather than advertisers. DOJ attorney Aaron Teitelbaum explained that publishers’ experiences, such as frustrations with DFP and AdX, provided clear evidence of anticompetitive practices stemming from Google’s ad network dominance. He noted that ad agencies, not advertisers, typically navigate Google’s tools.

When asked how the DOJ would proceed if the court accepted Google’s single-market definition, Teitelbaum argued there is still evidence of monopoly power. For example, Google’s Unified Pricing Rules (UPR) forced publishers to apply consistent pricing across ad platforms, a policy he said only a monopolist could enforce.

Google’s Refusal-to-Deal Argument

Google’s second major defense hinges on a 2004 Supreme Court ruling in Verizon v. Trinko. That decision broadly upheld Verizon’s right to deny competitors access to its network, setting a precedent that companies are generally not obligated to assist rivals. Google contends that its ad tech products already work with competing systems and that forcing further interoperability would effectively turn its advertiser base into “community property.”

The outcome of the case could have significant implications for the future of online advertising and Google’s role in it.