A federal judge said this 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.