This book provides the first comprehensive analysis of unbundling and, in particular, ownership unbundling policies from the perspective of international economic law. It does so by focusing on the prominent example of the EU's energy sector and its Third Energy Package. Unbundling has become an increasingly crucial competition instrument in network-bound industries worldwide. It is designed to ensure access to bottleneck infrastructures on fair and non-discriminatory terms and thus to suppress the anti-competitive potential deriving from vertical integration in natural monopoly situations. While promoting important public policy objectives, unbundling policies have also raised a number of legal issues. This book analyzes how international economic law limits the adoption and maintenance of unbundling and related measures and also outlines how international trade law can play a 'positive' role in this field. As a result, it provides a valuable reference for academics, practitioners and policy-makers.