The Law Lords in `Factortame' based their acceptance of the supremacy of European Community law on an 'entirely voluntary' surrender of sovereignty by Parliament. This interdisciplinary study tells the story, from the parliamentary perspective, of how Parliament's sovereignty came to be lost. It charts the evolution of MPs' constitutional understandings by analyzing the parliamentary debates on UK attempts to join the Community, the passage of the 1972 Act and the approval of subsequent Treaty revisions. The book's pervasive theme is the transformation from a UK constitution based on politics to one based increasingly on law. It assesses the extent to which MPs understood that EC membership entailed a shift in power from legislature to courts. This is a study with profound implications for the legitimacy of Parliament as a law-making body.The book also offers two comparisons. First the understandings of British MPs are contrasted with those of Irish parliamentarians, to establish whether Ireland's more law-based constitutional culture had an effect on politicians' understandings of EC implications. Secondly, the book analyses the history of the Bill of Rights debate culminating in the passage of the Human Rights Act 1998, to investigate whether (and why) themes of parliamentary sovereignty and judicial empowerment were clearer in this context than in the EC context.