For almost a decade the European Union has been stuck in a permanent crisis. Starting with domestic constitutional crises, followed by an imported financial crisis, it has evolved into a fully formed political crisis. This book argues that none of the crises are exclusively internal to the EU and the responses to date, which have taken inward looking approaches, are simply inadequate. Resolution can only come when the EU engages more fully with transnational law. This highly topical book offers an innovative dual focus on both transnational and EU law together. It sets out the relationship between the two frameworks by exploring practical concrete problems that transnational law has posed to the EU. These problems are explored from the perspective of four key tenets of both systems, namely the rule of law, democracy, the protection of human rights, and justice. It does this by advancing the theoretical framework of principled legal pluralism. In so doing it offers clear normative guidance as to how the relationship between EU and transnational law should be developed and fostered.