This is an open access book. What is the history and current state of play of EU law and policy covering irregularised human mobility? What has been the role and contributions of the 2019-2024 European Commission as regards EU migration policy? This book investigates how migration policies have been problematised at the EU institutional level, in particular by the European Commission. It critically assesses the assumptions lying behind the Commission's political priorities, agendas and policy outputs. Through the concept of irregularity assemblages, the book examines how EU policy professionals and bureaucracies in the relevant Commission services problematise their respective mandates/portfolios; how they interact with each other and even compete; and how they frame certain forms of human mobility as being an 'irregular migration problem' or not. After retracing key historical developments in the framing of irregularised human mobilities at the EU level, the book identifies six policy approaches in the work and structures of the 2019-2024 European Commission. It finds that a home affairs and criminalisation approach that prioritises a law enforcement understanding of cross-border and intra-EU mobility, and pursuing a Ministry of Interior-like agenda, has prevailed. This approach stands at odds with human dignity and other legitimate public policy approaches, such as those giving priority to employment and social inclusion, non-discrimination, and fundamental rights, where the administrative migration status of the individual is not the entry point. The overriding priority driving EU migration policy has been the expulsion, policing and criminalisation of people framed or categorised as 'irregular migrants'. The analysis shows how Commission has failed to effectively perform its role as guardian of the Treaties and unequivocally enforce and comply with EU Treaty constitutive values, EU law and Better Regulation commitments in migration policies.