This single case study researches the preferences of the actors identified by the two leading theories of EU (legal) integration: liberal intergovernmentalism and neo-functionalism. The preferences...Show moreThis single case study researches the preferences of the actors identified by the two leading theories of EU (legal) integration: liberal intergovernmentalism and neo-functionalism. The preferences guided us to derive a conclusion on which theory can best explain the termination of intra-EU bilateral investment treaties (BITs). This provided new building blocks to the ongoing discussion of the theories contrasting approaches to EU integration. The methods used in this study are document analysis and within-case causal process tracing to uncover the different steps of the actors to measure their preferences. Liberal intergovernmentalism states that the EU member states’ preferences are the steering factor of legal integration as they are the masters of the EU treaties and the only actors that can alter them. The EU organs act as the agents of the states and are reactive to them. Neo-functionalists explain that individual actors and their self-interests determine integration. They form interest groups on the national and supranational levels and create spillover effects. Furthermore, as the EU agenda setter, the European Commission (EC) is a central actor in explaining EU legal integration. This study found convincing evidence that especially the EC was a significant steering factor in explaining the termination. Overall, the interest groups’ preferences from the supranational level picked up the economic needs of the national level and supported the termination of intra-EU BITs for a change to an EU-wide system to reduce transaction costs and boost the EU economy. This study argued that the member states reacted to these actors. Therefore, this study concluded that neo-functionalism is perceived as the better theoretical approach to explain the termination of intra-EU BITs.Show less