This book sets out to explain the drivers shaping cooperative patterns on the readmission of unauthorised third-country nationals, whether at bilateral or EU level. It lays emphasis on the existence of a predominant bilateral readmission system in which EU agreements are inextricably embedded. As a result of the entry into force of the Treaty of Lisbon, the reinforced political control of the European Parliament calls for an analysis of this system and of its implications for human rights observance.