A federal judge said last week that the Justice Department and a group of states could not move forward with some claims in an antitrust lawsuit against Google, narrowing the scope of the most significant federal monopoly trial against a tech giant in decades.

In the decision, which was unsealed on Friday, Judge Amit P. Mehta of the U.S. District Court for the District of Columbia said the U.S. government and the states could not argue that Google maintained a monopoly by boosting its own products in search results over those of specialized sites. They had not “demonstrated the requisite anticompetitive effect,” he said.

But Judge Mehta declined Google’s request to dismiss portions of the case. The government can continue to make its other central claims, he said, including that Google broke the law with agreements that ensured it would be the default search engine on mobile browsers and that its search apps would be preloaded on smartphones.

The decision sets the stage for the first major tech monopoly trial since the federal government took Microsoft to court in the 1990s, accusing it of monopolistic practices. In recent years, American regulators have worked to rein in the power of tech giants like Google, Amazon, Apple, Microsoft and Meta, which owns Facebook and Instagram, filing lawsuits arguing that the companies have abused their monopolies and trying to block their acquisitions of other companies.

Kent Walker, Google’s president of global affairs, said in a statement that the company appreciated Judge Mehta’s “careful consideration and decision to dismiss claims regarding the design of Google Search.” The Justice Department did not immediately respond to a request for comment.

The Justice Department filed the antitrust case against Google under President Donald J. Trump in 2020. It argues that the Silicon Valley company exploits its power over online search and the ads that appear in search results. It was ultimately combined with a separate case, also about Google search, that state attorneys general had filed.

The case is scheduled to go to trial on Sept. 12, potentially kicking off years of courtroom battles over monopoly claims filed against the tech giants.

The Justice Department has separately filed another antitrust case against Google, focused on the company’s software for placing ads across the web, which is headed to trial as soon as next year.

Some efforts by regulators to challenge the tech giants have faltered in the courts. Twice this year, federal judges have declined to grant Federal Trade Commission requests to stop tech deals, allowing Meta to close its purchase of a virtual reality start-up and clearing the way for Microsoft’s blockbuster acquisition of the video game publisher Activision Blizzard.

At the trial for the Google monopoly case, both sides are set to argue over whether the company’s multibillion-dollar agreements to be the default search engine on various devices and browsers are anticompetitive, which could have significant consequences for its core business. Google’s search engine collected $162 billion in advertising revenue last year.

Google has argued that these pacts with companies like Apple and Samsung are simple distribution deals that are common in business, and that the government has tried to penalize Google because of its popularity.

The agreements have been a linchpin in Google’s efforts to be easily accessible to large audiences. The company retains an estimated 94 percent of search engine traffic on mobile devices, according to Similarweb, a data analysis firm.

David McCabe and Nico Grant are reporters with The New York Times. Copyright 2023, The New York Times.