As the threats posed by organised crime and terrorism persist, law enforcement authorities remain under pressure to suppress the movement, or flows, of people and objects that are deemed dangerous. This collection provides a broad overview of the challenges and trends of the policing of flows. How these threats are constructed and addressed by governments and law enforcement agencies is the unifying thread of the book. The concept of flows is interpreted broadly so as to include the trafficking of illicit substances, trade in antiquities, and legal and illegal migration, including cross-border travel by members of organised crime groups or 'foreign fighters'. The book focuses especially on the responses of governments and law enforcement agencies to the changing nature and intensity of flows. The contributors comprise a mix of lawyers, sociologists, historians and criminologists who address both formal legal and practical, on-the-ground approaches to the policing of flows. The volume invites reflection on whether the existing tool kit of governments and law enforcement agencies is adequate in this changing environment and how it could be modernised, for example, by increased reliance on technology or by reappraising the role of the private sector. As such, the book will be useful not only for academics and practitioners who work on security-related matters, but also more generally to those who are interested in what the near-term future of policing is likely to look like and how the balance between law enforcement on the one hand and human rights and civil liberties on the other can be achieved.