This book examines the growing divergences between the EU and the US in their approach to antitrust law enforcement, particularly where it relates to intellectual property (IP) rights. The scope of US antitrust law as defined in the Supreme Court's decisions in Trinko and Credit Suisse Securities is much narrower than the scope of EU competition law. US antitrust enforcers have become increasingly reluctant to apply antitrust rules to regulated markets, whereas the European Commission has consistently used EU competition rules to correct the externalities resulting from government action. The contrasting approaches adopted by US and EU antitrust enforcers to these issues, as with the differences in addressing market dominance, have had a profound impact on the scope of antitrust intervention in the IP field. This book provides an in-depth analysis of the relevant recent developments on both sides of the Atlantic and identifies the pitfalls of regulating IP through competition rules. With a unique comparative perspective, this book will be an invaluable resource for postgraduate students, academics and practitioners in IP and competition law.