A federal court today rejected a proposal by the U.S. Justice Department to break up Google LLC’s ad business. The ruling came in connection with an antitrust lawsuit that began more than three years ago. In January 2023, the Justice Department and several state attorneys general sued Google LLC over its display advertising unit. The unit helps brands purchase ad space on third-party websites. The complaint charged that Google used anticompetitive practices to maintain a dominant position in that market. Last April, the U.S. District Court for the Eastern District of Virginia ruled in favor of the Justice Department. U.S. District Judge Leonie Brinkema found that Google’s display advertising business maintains an illegal monopoly. Prosecutors argued that the best way to remediate the situation is to sell off parts of the business. However, Brinkema rejected that line of reasoning in today’s ruling. The Justice Department wanted Google to sell off a now-defunct display advertising service called AdX. It’s an online auction where brands bid for ad space on publishers’ websites. The service was the core focus of the antitrust lawsuit that kicked off the litigation. Website operators historically put their ad space up for sale on AdX through a second,...