National implementation constitutes a key element in ensuring compliance with international environmental law. It plays a dominant role in ensuring non-state actors' compliance with international environmental norms, particularly where international environmental law has been translated, directly or indirectly, into national law. It may also afford opportunities for non-state actors to successfully challenge national implementation of international environmental law through judicial review, national rules on standing and remedies permitting. This article considers the trends in domestic judicial enforcement, and the role that national courts play in both developing and enforcing international environmental law. It also examines the nature of the international norms in question, as well as the impact that this factor exerts on national implementation (both legislative and judicial), drawing upon the extensive literature on implementation and compliance with international environmental law. Finally, the article looks at the extent of reliance upon national measures of implementation under different treaties, the impact of domestic constitutional legal orders on implementation, and soft law instruments.