Since the 1972 Conference in Stockholm, United Nations members acknowledged that a straight, cohesive and coherent environmental action must be at the centre of the international political agenda. The evolution of this path towards a global environmental consciousness fostered the establishment of several principles that represent the ‘backbone’ of current international and domestic legal efforts to cope with environmental issues. The recognition of international environmental principles does not automatically lead to the implementation and the enforcement of environmental provisions. As a response to this lack of effectiveness, national legal systems have undertaken constitutional recognition of the environment. In spite of the hypothetical existence of a global constitution, a key question is whether domestic constitutional law could be considered as the most suitable legal arena for both theoretical and pragmatic responses to environmental concerns. Considering the aforementioned theoretical questions, the chapter introduces the international environmental law regime and its body of principles, further discussing their national recognition and implementation. To this end, the analysis focuses on environmental constitutionalism and assesses the different scholarly approaches according to three perspectives, namely the ‘good’, the ‘bad’, and the ‘ugly’, with the aim of addressing whether there are competitive or cooperative influences between international environmental law and environmental constitutionalism.