One of the greatest objects of judicial activity and academic commentary in European Union (EU) law has been the free movement of goods. The free movement of goods continues to generate intense debates because it is at the intersection of complex and difficult choices between public regulation and market freedom, on the one hand, and EU and state powers on the other. This chapter provides an overview of such debates and how they affected the development of EU law on the free movement of goods. It uses the General Agreement on Tariffs and Trade (GATT) to identify some specificities of the European system. Under the GATT, discrimination tests are preceded by a market equivalence analysis of the relevant products, requiring an economic and empirical analysis of the market prior to determining whether the products are subject to differentiated treatment.