This book examines the gradually increasing role of national parliaments in the European Union and asks how and why this came about. It takes Ireland as a case study, examining the relationship between Ireland’s parliament (the Oireachtas) and the European Union. It also focuses sharply on parliament’s role in European affairs in Ireland, a jurisdiction of strong comparative interest to the UK . It examines the evolution in national parliaments’ roles, the reasons for change and the challenges that must be faced in making further progress. The book analyses Ireland’s slow parliamentary adaptation to European integration, analyses the impact of the Lisbon Treaty and economic crises in accelerating reform, and identifies where improvement is still badly needed.