The book examines how the interests of the member states, which provide the primary driving force for developments in European integration, are internalised and addressed by the law of the European Union. In this context, member state interests are taken to mean the policy considerations, economic calculations, local socio-cultural factors, and the raw expressions of political will which shape EU policies and determine member state responses to the obligations arising from those policies. The book primarily explores the junctions and disjunctions between member state interests defined in such a manner and EU law, where the latter expresses either an obligation for the member states to comply with common policies or an acceptance of member state particularism under the common EU framework.