It has long been a commonplace that the European Union forms a community of law and that the principle of “integration through law” is one of its central characteristics. In view of the growing scope and complexity of Union law, which requires ever new adaptations from the Member States, research on the implementation of Union law, which also works empirically, is gaining considerable importance. An international research project conducted at the German Research Institute for Public Administration was dedicated to the implementation and adaptation strategies of selected EU Member States. It investigated the transposition of organisational and procedural requirements for national administrations as laid down in EU directives related to environmental and energy policy. The investigation focused on various modalities of transposition: minimum transposition (“copy out”), the enactment of provisions that create obligations going beyond the requirements of the Directive (“gold-plating”) and the extension of the rules or principles of the Directive to other fields of law (“spill-over”), either by including a subject area not provided for in the Directive in the scope of application of the transposition provisions (spill-over in the narrow sense) or by fundamentally reforming a legal area on the occasion of the Directive (spill-over in the broad sense). The comparative analysis revealed a low degree of strategic use of transposition modalities. However, there is a growing awareness among Member States that they belong not only to a law community, but also to an implementation community. This is not least due to the mechanisms and procedures of intertwining Union and national action.