The previous two chapters have explored the EU Presidency's capacity to shape political outcomes as agenda manager and broker. This chapter turns to the third and final of the Presidency's key functions – representing the member states in negotiations with third parties. The EU Presidency negotiates on behalf of member governments in two principal contexts. It functions as the Council's representative in inter-institutional negotiations with other EU bodies. In particular, it engages in legislative negotiations with representatives of the European Parliament as part of the co-decision procedure, the dominant legislative procedure in the EU. Furthermore, the Presidency acts as the member states' representative in certain international negotiations. The area where the function as external negotiator is most institutionalized is accession negotiations with countries that wish to become members of the EU.

The central argument in this chapter is that EU governments' engagement of the Presidency as their representative leads to a classic principal–agent problem, with divergent preferences, incomplete control, and agent discretion. This claim shares important affinities with arguments about delegation and agency in other contexts where collective principals have delegated powers of representation to an executive agent, for instance, international trade negotiations. In the EU, the member governments have delegated the authority to negotiate agreements to an actor with its own interests and stakes in the outcome. Simultaneously, they have refrained from establishing mechanisms of complete control, since the Presidency must be able to negotiate with some flexibility in order to arrive at external agreements.