This chapter examines economic and trade theory as well as the politics and the evolution of global trade governance in practice. When viewed from the perspective of methodological individualism, international trade can be seen as the aggregate of the billions of cross-border transactions that take place between willing buyers and willing sellers located in different countries daily. Governments can either get in the way by erecting tariff or non-tariff barriers or get out of the way by allowing free trade. While the signing of the General Agreement on Trade and Tariffs (GATT) in 1947 and successive negotiation rounds have led to reduced tariff non-tariff barriers, there is a discussion of why the World Trade Organisation (WTO) has found it difficult to get countries to agree to further trade liberalisation. The politics behind protectionism and the opposition to further trade liberalisation is explained by reference to public choice and principal agent theories.