WASHINGTON (Reuters) -Alphabet's Google broke the law with its monopoly over online searches and related ads, a federal judge ruled on Monday, in the U.S. Justice Department's first victory against a monopoly in more than 20 years.

The decision is a significant win for the Justice Department, which had sued the search engine giant over its control of about 90% of the online search market, and 95% on smartphones. The judge noted that Google had paid $26.3 billion in 2021 to ensure that its search is the default on smartphones and browsers, and to keep its dominant market share.

"The court reaches the following conclusion: Google is a monopolist, and it has acted as one to maintain its monopoly," U.S. District Judge Amit Mehta wrote.

Mehta's ruling against Alphabet's major revenue driver paves the way for a second trial to determine potential fixes, such as requiring the company to stop paying smartphone makers billions of dollars annually to set Google as the default search engine on new phones.

The ruling is the first major decision in a series of cases taking on alleged monopolies in Big Tech.