Alphabet Inc.’s Google has been found to have unlawfully dominated key online advertising markets, a federal judge ruled on Thursday, marking another setback for the tech giant in a growing antitrust case brought by the U.S. government, Reuters reported.

U.S. District Judge Leonie Brinkema, in a decision handed down in Alexandria, Virginia, determined that Google monopolized both the publisher ad server market and the ad exchange market, the report said. However, Judge Brinkema reportedly ruled that antitrust enforcers had not proven that Google held a monopoly in the advertiser ad networks market.

The ruling could have wide-reaching implications for Google’s business practices, particularly in its advertising products. Reports suggest it opens the door for the U.S. Department of Justice (DOJ) to argue for the company’s breakup, a move that would likely involve forcing Google to divest its Google Ad Manager, which combines both its publisher ad server and its ad exchange.

The decision comes as Google is already facing pressure from two U.S. courts. Next week, a judge in Washington will hear a separate case on the DOJ’s request for Google to sell its Chrome browser and implement other measures to reduce its dominance in online search.

Google has reportedly considered selling its ad exchange in the past to appease European antitrust regulators, according to a Reuters report from September.

Brinkema’s ruling stems from a three-week trial held last year, during which the DOJ and a coalition of states accused Google of using classic monopolistic tactics, the report further said, adding that prosecutors argued the company eliminated competitors through acquisitions, locked customers into its ecosystem, and controlled the way transactions occurred in the online ad market.

In response, Google defended its actions by claiming that the case focused on the company’s past behavior, when it was still developing tools to integrate with competitors. Google’s lawyers also reportedly pointed to competition from other tech giants, including Amazon and Comcast, as factors that prosecutors overlooked. They argued that digital ad spending had shifted to mobile apps and streaming video, areas where Google’s dominance was not as strong.