This book is a study of immigration administration and administrative law in context. It considers the mission, history, politics, and organisation of immigration administration from an administrative law perspective. The book critically examines in detail how the immigration department performs its core functions – making policy and rules, taking casework decisions, and enforcing immigration controls. It also examines how the department is structured, organised, and held to account. The book adopts an administrative law in action approach and examines aspects of internal administrative law. It undertakes this examination by blending empirical and theoretical administrative law analysis. The conceptual framework constructed for this end draws upon the concepts of instrumental rationality, organisational competence and institutional design.‘Fresh, challenging and department-centred, this book is an important contribution to contemporary administrative law scholarship. Interweaving theory and principle with careful analysis of legal and administrative practice, Robert Thomas takes us on an eye-opening journey through the heavily contested field of immigration administration. Bravo!’ (Richard Rawlings, Professor of Public Law, UCL).