This chapter confronts what Björn Hettne (2005) has described as the ‘ontological problem’ of dominant approaches to regionalism and international economic law. These theories tend to be mono-disciplinary, focusing on one mode of knowledge production, such as economics or politics, and thereby privilege certain research questions at the expense of others (Hettne, 2005: 543). They provide atomised accounts of economic action, in which the international legal system appears as fixed and determinable. By contrast, this chapter draws on economic sociology to reconceptualise economic activity, and its laws, as embedded in social life. It does so using the example of the inter-regional agreement between the European Union (EU) and the Southern Africa Development Community (SADC), known as the EU-SADC Economic Partnership Agreement, and its interaction with provisions of a multilateral agreement, in particular Article XXIV of the General Agreement on Tariffs and Trade (GATT) administered through the World Trade Organization (WTO).