This book examines the gradually increasing role of national parliaments in the European Union (EU) and asks how and why this came about. Using Ireland as a case study it delves into the relationship between the Oireachtas and the EU. This is a pioneering study of parliament's role in European affairs in Ireland - a jurisdiction of interest in its own right but also a comparator for the UK, which, even after Brexit, will need Parliament to play a strong role in exacting accountability from the Government in European affairs. It looks at the evolving role of national parliaments over time, examines the reasons why change has happened and derives lessons for future development. It considers the arguments both in favour of, and against augmenting the influence of national parliaments in European affairs. It examines the challenges that must be confronted in any effort to build on the current role of national parliaments in EU affairs. The book analyses the painfully stop-start yet real process of Irish parliamentary adaptation to European integration, analyses in particular the impact of the Lisbon Treaty and banking and sovereign debt crises in driving reform, and describes where matters stand now - and where improvement is still badly needed. The evolving role of national parliaments in the European Union will be of interest to those academics and students studying law, political science, (particularly democracy and parliamentary studies), European studies, and European and constitutional law.