Thomas Greaney and Samuel Miller—both adjunct professors at UC Hastings College of the Law and former attorneys with the Antitrust Division of the US Department of Justice—describe how antitrust law in the United States no longer operates as a legal sword to keep markets competitive, but as a shield to protect large companies from competition. Greaney and Miller call for a renewal of the antitrust enterprise using the best of current economics informed by a realistic appreciation for how markets actually work in the real world.