The book is the extended version of the inaugural lecture given by Professor Petra Bárd on 21 September 2023 on the occasion of her taking up the Chair in Sustainable Rule of Law at the Research Centre for State and Law (SteR) in the Faculty of Law at Radboud University, Nijmegen. Professor Bárd places the specific manifestation of rule of law deficiencies in the evolution of European criminal justice within a broader constitutional context. She has led the way in reframing the academic and policy debates, so that mutual trust and mutual recognition, the principle guiding EU criminal cooperation, are firmly grounded in the framework of defending and sustaining the inextricably linked values of democracy, the protection of fundamental rights and the rule of law. The inaugural lecture, just like the award of the Chair, is a testament to Professor Bárd’s immense contribution towards understanding and defending the rule of law in Europe in challenging times. Professor Valsamis Mitsilegas Foreword by Kim Lane Scheppele; Foreword by Valsamis Mitsilegas; Rule of law sustainability and mutual trust in a transforming Europe; I. Rule of law and criminal justice in the national setting; II. Rule of law sustainability at the supranational level; III. EU criminal cooperation: a canary in a coalmine; IV. The future: a race to the bottom or a two-tier Europe; V. Privilege and gratitude