Member State obligations in the EU are obligations which are undertaken jointly and voluntarily by the Member States in the service of their interests. The Member States expect that by undertaking these obligations they have enabled the realisation of the general and specific ‘objectives’ assigned to the EU. The latter are usually policy and other objectives they are unable to realise or realise adequately on their own. The joint commitments of the Member States in the EU rest on the political mandates of national governments, and their realisation often depends on competences, functions and capacities that are available at national level. Member State obligations are also obligations that are governed fundamentally, and in many particular aspects, by law. Construing these obligations as legal obligations has had the effect of separating Member State obligations from the interests held and pursued by them. Bringing in law to govern Member State obligations has also enabled laying down and controlling boundaries between legitimate and illegitimate conduct by the Member States in the EU. Overall, Member States’ interests provide a relevant framework for interpreting legal developments in the EU concerning Member State obligation, and enable a more sophisticated understanding and analysis of those developments.