This volume brings together research aimed at shedding light on a general problem, by focusing specifically on the services sector. In the WTO system, the services sector is regulated by the General Agreement on Trade in Services (GATS); in the European system, it is regulated by a broad and complex body of rules, combining judge-made principles with those embodied in the secondary legislation, which codifies and applies these principles to different regulated sectors.The general problem at the core of this study stems from the difficulty in striking a balance between two important needs. One the one hand, there is the need to recognise national authorities' right to autonomously regulate and govern in their own territory. On the other hand, there is the need to limit this power of autonomous regulation, mainly to protect the right of foreign economic operators to access the national market and function in conditions of equality with respect to all other operators.This problem is addressed from the particular perspective of administrative law. The premise underlying the various contributions is that supranational (global and European) law constrains domestic regulation (and domestic administrations) largely through techniques and procedures drawn from administrative law. Sovereignty-limiting procedures developed by national legal systems in order to protect citizens have been readapted by supranational public powers to protect the rights of foreign economic operators and to realise the goal of market integration.This administrative law perspective also gives shape to the structure of this volume, which is divided into three thematic areas. Each area corresponds to a category of constraints imposed by supranational administrative law upon States' right to regulate.The first area is the law of administrative procedure: here, the supranational law regulates the national decision-making process, often through techniques and procedures that are inspired by, and then superimposed upon, national administrative procedure.The second area is substantive administrative law, specifically the limits imposed by supranational administrative law upon the content of member States' regulatory decisions.The third area regards the rules governing national public powers' transfer of their right to regulate, rather than the supranational check upon the exercise of this right. To further economic integration, supranational public powers may pressure States to transfer their power to regulate in their own territory in both a vertical and horizontal direction: vertically, to supranational institutions, through techniques of harmonisation; horizontally, to other States, through techniques of mutual recognition.