The legal structures of market supervision vary widely across countries and market sectors. The European Union frameworks for supervising national supervisors show a remarkably similar taste for divergence. This project aims to increase oversight in those European Union aspects of supervision.In a first phase, the project will compare and contrast the European Union's legal organisation of market supervision in three different market sectors. It will consider the decentralisation of European competition law supervision, the centralisation of European financial supervision and the approaches to supervision in liberalised markets, more specifically in the market for railway transport. Throughout the comparison of those approaches, this phase aims at analysing the specificities of sectored supervisory structures. In addition, it will propose possible improvements to specific supervisory problems in light of experiences and alternative structures in different supervisory sectors.The second phase of the project will analyse the abovementioned supervisory structures in light of the foundations of the Internal Market and the search for a European economic constitution. Market supervision will be considered a means to market integration and the different supervisory approaches will be analysed from that point of view. The aim of this research phase is not to design an optimal European supervisory model. Rather, it aims to contribute to the incorporation of supranational supervision in more general (economic) theories about European federalism and market regulation.