The European Court of Justice has been alluding to 'abuse and abusive practices' for more than thirty years, but for a long time the significance of these references has been unclear. Few lawyers have examined these references and those that have doubt whether these references amount to the development of a general principle. Within the last few years, this state of affairs has changed radically, largely due to the development by the Court of an abuse test in Emsland-Starke, a case concerning agricultural products which was decided in 2000, and the subsequent emergence of an intense debate as to whether the Court would apply this new test within the field of taxation. More recently, the rulings in Halifax and Cadbury Schweppes, the former applying the abuse test to VAT, the latter to corporate taxation, represented a definitive turning point in terms of the attention that both commentators and practitioners alike have paid to the newly designated 'principle of prohibition of abuse of law'. This new work presents the papers presented at an Oxford symposium on the subject, providing an opportunity to discuss the development of the Court's approach to abuse of law, analysing the case-law from the 1970s to the present day, and enquiring as to the consequences of the introduction of a new EU law principle of prohibition of abuse for the development of the laws of the EU and the Member States.