As the European Union matures, there is an increasing debate - partly fuelled by fierce national criticism offered by Eurosceptic politicians, partly initiated by the EU institutions themselves - on the way in which the EU has developed and what the EU must look like in the future. This debate includes a discussion on one of the core aspects of European integration: at which level should the rules be set and who decides where the authority to do so should lie? Private law has an important role to play in this discussion. Many private law rules touch on the core of the internal market, as they...