By Sophie Lindqvist

A US federal judge has ruled that Google broke the law to maintain its advertising monopoly, delivering the company its second major antitrust defeat in under a year.

The decision, published in 2025, came from a federal court handling the advertising technology case brought by the US Department of Justice. The judge found that Google unlawfully protected its dominant position in the digital advertising market.

What did the court decide?

The court sided with the government. It ruled that Google violated antitrust law — the body of US law that prohibits companies from maintaining monopoly power through exclusionary conduct rather than competition on the merits.

The holding is simple to state: Google broke the law to keep its advertising monopoly. That single sentence carries enormous weight. It confirms the Justice Department's core theory of the case. The government argued Google controlled the essential machinery of online advertising and used that control to lock out rivals.

This matters because it is not Google's first loss. The company already lost a separate search monopoly case. Two federal rulings against the same defendant, in two different markets, within roughly a year. That pattern reshapes how courts and regulators view Big Tech.

Why is advertising technology the battleground?

Online advertising runs on intermediaries. Google sells tools on both sides of the trade. It acts as seller for publishers, buyer for advertisers, and runs the exchange in between. Think of one company owning the auction house while also representing most of the bidders and the goods.

The Justice Department said that structure gave Google an unassailable advantage. Rivals couldn't compete for ad transactions when Google sat at every chokepoint. The court agreed the company crossed from lawful dominance into unlawful monopolizing.

What happens next?

The ruling triggers a remedies phase. That means the court will now decide what punishment or structural fix to impose. Options typically include behavioral restrictions or, more dramatically, forced divestitures — selling off parts of the business.

For practitioners, the immediate consequence is procedural. Google will fight the findings and any remedy. Appeals are near certain. But the legal risk has shifted: Google must now argue about remedies and appellate standards, not about whether it violated the law at all.

For advertisers and publishers, the ruling could eventually loosen Google's grip on ad transactions. Any divestiture of ad tech assets would restructure a market worth tens of billions of dollars annually. Nothing changes immediately, though. The current system stays in place during the remedies and appeals process.

How does this fit the wider antitrust picture?

The decision lands amid a wave of US enforcement against major technology platforms. Google's earlier search case loss, plus parallel actions against other tech giants, signals a more aggressive posture from Washington.

Each ruling builds on the last. Courts grow more comfortable applying century-old antitrust statutes to digital markets. The Google ad tech decision reinforces that trend. It shows the government can win on liability, not just bring cases.

For the legal profession, expect a surge of follow-on work. Private plaintiffs will cite the finding in damages suits. Clients in adjacent digital markets will want risk assessments. And every dominant firm with intermediary businesses — marketplaces, exchanges, platforms — will revisit its exposure.

The bottom line: a federal judge has ruled Google broke the law to keep its advertising monopoly. The fight now moves to consequences.