Competition Law As Common Law: American Express and the Evolution of Antitrust

We explore the implications of the widely accepted understanding that competition law is common — or “judge-made” — law. Specifically, we ask how the rule of reason in antitrust law should be shaped and implemented, not just to guide correct application of existing law to the facts of a case, but also to enable courts to participate constructively in the common law-like evolution of antitrust law in the light of changes in economic learning and business and judicial experience. We explore these issues in the context of a recently decided case, Ohio v. American Express, and conclude that the Supreme Court did not apply the rule of reason in a way that enabled an effective common law-like evolution of antitrust law.