This book explains the functioning of shared competences in environmental protection by focusing on member states' interaction with the EU framework. By studying this interaction, Squintani reveals room for improving the level of environmental protection, legal certainty, and efficiency of the system for environmental protection envisaged under the EU Treaties. Accordingly, this book makes a contribution to EU environmental law and policy, but also should be of interest to constitutional lawyers more generally and to scholars working in any field of EU policy and law in which minimum harmonisation is used. Thanks to its focus and clear, accessible prose, this book is also valuable additional reading material for environmental law courses, and to those involved in decision-making in the EU.