The Substantive Law of the EU provides a critical and thorough analysis of the key principles of the substantive law of the EU, focusing on the four freedoms (goods, persons, services, and capital). An introductory chapter provides valuable context on the nature of the internal market, its evolution, and the theories behind its key principles. Each of the freedoms is then considered in turn. The book concludes with a discussion of harmonization, the regulation of the internal market, and its future.