Can Google avoid a breakup twice?

In a landmark decision this month, a federal judge spared Google from a breakup proposed by the government to rein in the company's monopoly in search.

Now, the company wants a second win.

Starting Monday, Judge Leonie M. Brinkema will hear arguments in the US District Court for the Eastern District of Virginia on how to fix Google's monopoly over some online advertising technology.

The judge ruled this year that Google had broken the law to protect its dominance over the largely invisible system of technology that places ads on pages across the web. The hearing is expected to last for two to three weeks.

The Justice Department has said it wants Google to sell the technology it uses to connect buyers and sellers of ad space, among other potential remedies. Google has instead proposed measures including changing its ad auction bidding system in ways that would benefit publishers.

Brinkema's ultimate decision could disrupt the company's $3.1 trillion business and help rewrite the playbook for tech dominance in the modern internet era.

She has already indicated she might do so, asking during a May hearing whether forcing the sale of one of Google's advertising software products could resolve her concerns. The case also aligns more closely with past tough antitrust decisions, which could make it easier for the judge to take an aggressive tack, legal experts said.

The hearing comes after a conservative antitrust decision by Judge Amit P. Mehta of the U.S. District Court for the District of Columbia this month in the search monopoly case, in which he ruled Google's search business could essentially continue operating as is. The company must share its search results with rivals and restrict payments that ensure its search engine gets prime placement in web browsers and on smartphones. But Mehta did not approve the government's request that Google be forced to sell its popular Chrome web browser, alongside other harsher penalties.

The decisions in the cases against Google could factor in the outcome of other government antitrust lawsuits against the biggest tech companies. A judge is expected to rule this year on a lawsuit against Meta, in which the government argued the company snuffed out nascent competitors by buying Instagram and WhatsApp.

A lawsuit against Amazon, in which the government accuses the company of squeezing the small merchants using its platform, is scheduled for trial in 2027. The government also sued Apple, accusing it of making it difficult for users to leave its ecosystem of devices.

Lee-Anne Mulholland, the global head of regulatory affairs at Google, said in a statement that the Justice Department's proposal for fixing ad technology went too far and would "unwind acquisitions the Court found to be lawful, and risk breaking tools that work for advertisers and publishers."

The Justice Department did not offer additional comment.

A breakup of Google would be the most significant action taken by a court against a monopoly since a federal judge tried and failed to split Microsoft 25 years ago. The last successful attempt dates back to 1984, when AT&T's local phone business was split into seven regional operators after settling with the government.

The ad tech case -- U.S. et al. v. Google -- was filed in 2023. It concerns an intricate web of programs that sell ad space around the web, like on a news site or a recipes page. The suite of software conducts split-second auctions to place ads each time a user loads a page.

That business made $30.36 billion in 2024, or about 9% of the total revenue for Google's parent company, Alphabet. Google has an 87% market share in ad-selling technology, according to the government.

Publishers and rival ad tech companies testified in a three-week trial last year that Google used its dominance to take a bigger cut of ad sales than possible in a competitive market.

The Justice Department argued that Google had a monopoly over three parts of the online advertising system: the tools publishers use to host their ad inventory, the system advertisers use to place their bids for that ad space and the technology that connects the two sides of the transaction.

Google countered that the advertising industry had changed. The ads placed on websites were part of a larger ecosystem that included ads on streaming sites and social media platforms like TikTok, the company argued.

Brinkema agreed with the government that Google had a monopoly over the publisher tools and the technology that facilitates the sales. The company had maintained its monopoly in part by tying the two systems together, she said.

But the government did not prove that Google had broken the law when it came to the tools for advertisers, she said, and that its ad tech acquisitions were not anticompetitive on their own.

Now, witnesses, including current and former Google employees, and experts will testify on how to address that monopoly power.

The Justice Department has asked Brinkema to force Google to sell the software that connects buyers and sellers of ad space, known as an ad exchange. It also wants to force the company to provide some of the code that runs ad auctions to its competitors. If competition does not improve after these steps are taken, the government also wants an independent monitor to determine whether Google must sell more of its publisher tools.

Google has proposed that it take measures to open its ad software to competitors. Google's ad exchange could connect directly with ad tools for publishers made by rivals. And it could change rules for ad auctions that rivals said gave Google an advantage over its competitors.

During the May hearing, Brinkema hinted she was weighing the government's argument to force a sale of its ad exchange.

"If you get rid of the exchange, which is the connector between those two, you no longer tie the publishers in that respect, and the advertisers can go out and use any exchange that they want," she said. "Google can't do anything to try to sabotage that free exercise of choice. Why would that not work?"

Brinkema's decision will tilt the scales on antitrust law enforcement, legal experts said.

That Google was found to be a monopoly in both search and ad tech was "a relief for everyone who argued that the laws on the books are sufficient" enough to rein in the biggest tech companies, said Doha Mekki, the former acting assistant attorney general for antitrust during the Biden administration.

"If the remedies fail to address the very serious and pernicious monopoly problems that have been found, I think it raises a question about whether this part of the law is sufficient to police digital markets," added Mekki, who oversaw portions of the ad tech litigation.