This conclusion presents an overview of key concepts discussed in the preceding chapters of this book. The book presents the European Union as the only contemporary example of a regional organisation which has moved beyond mere cooperation in the environmental sector to reach a degree of integration marked by legal pervasiveness and specialised regulation. It clarifies the role of regional organisations in the development of closer institutional linkages among neighbouring countries on the basis of shared values, principles and legal traditions. The New Zealand Biosecurity Act was only approved in 1993, meaning that simple biological control gave way to a more comprehensive approach encompassing economic, social, cultural and environmental aspects. The choice of a case that – for geo-political and socio-economic reasons – seems to be so antipodal with respect to the European Union is explained by the role of New Zealand as a forerunner in the protection of native flora and fauna from threats coming from invasive alien species.