The Council is a crucial intergovernmental institution of the European Union. However, the complex, opaque and consensual character of the decision-making process in the Council puts its legitimacy into question. Intergovernmentalist theory posits that it is sufficiently legitimised, indirectly, by the member state governments. Constructivist research, on the other hand, suggests that socialisation might disturb the relaying of positions from the national to the supranational level, as the former approach implies. This paper aims to explore these issues, in particular related to representation and consensus. It contains an analysis of material generated in in-depth interviews. The Capital Markets Union (CMU) initiative serves as an umbrella term for regulatory changes directed at the overall development of European capital markets. As such, when analysing the legal framework of the CMU, it is important to note that this involves an undertaking which goes beyond the regulation of financial systems, also aiming to achieve supervisory convergence throughout the member states of the European Union. Indeed, it is perhaps one of the clearest examples of federal implications within the EU. All the synchronous movements enacted into law, leading towards harmonisation and supervisory convergence, show us that the CMU is an foundational piece in a collective journey towards ever greater integration in terms of economic governance and economic policies. Nonetheless, even if the CMU is one of the few cross-country risk-sharing mechanisms available to the EU, its implementation faces difficulties (as well as the looming Brexit) that demand careful analysis.