This book examines how national law is treated in WTO law, both in the WTO treaty and dispute settlement cases. The WTO treaty contains a set of far-reaching obligations establishing a systemic and constitutional framework of interaction between WTO law and national law. WTO dispute settlement operates as an international layer of judicial review of national laws and administrative, judicial or quasi-judicial measures. Consequently, much of the WTO dispute settlement decisions and rulings relate in different ways to Members' national laws. Yet, there is no systematic analysis of this vastly important subject. This book provides the first thorough map of an increasingly complex field. In doing so, it extends the enquiry beyond well-known formulas and combines practical analysis with principled discussion of how the treatment of national law in international law can and should ensure effectiveness of international rules and promote good governance within nation-states. Written in as non-technical way as possible, which will allow WTO experts and non-experts to easily understand the material presented, the book presents the reader with an understanding of a vastly important, yet underexplored subject area. For comparative analysis the book draws on general international law, EU law, European human rights law and the law of the North American Free Trade Agreement.