In the biggest antitrust case in decades, a federal judge ruled Monday that Google illegally maintains a monopoly over the online search industry, using its market dominance to shut out competitors and limit user choice. “Google is a monopolist, and it has acted as one to maintain its monopoly,” Judge Amit Mehta of the U.S. District Court for D.C. wrote in his ruling. What remedies will be demanded by the government is the next stage of the lawsuit, which is also likely to be appealed all the way up to the U.S. Supreme Court, says antitrust expert Matt Stoller. But the ruling is certain to have far-reaching effects in Silicon Valley as Big Tech firms face increasing scrutiny over their business practices. “The question has been: Who runs this country?” says Stoller. “Is it a small group of people that make choices about what we can see online, or is it the public, through competition?” Stoller is research director at the American Economic Liberties Project and author of Goliath: The 100-Year War Between Monopoly Power and Democracy.