The European Union (EU) is committed to the principle of solidarity, which is regarded as vital to the notion of a social Europe that is embedded in the European Charter of Fundamental Rights and is rendered legally binding by the Lisbon Treaty 2007. Connecting social and economic to civil and political rights, social solidarity is articulated by the Solidarity Chapter of the Charter, with articles that include ‘fair and just working conditions’, ‘social security and social assistance’ and the ‘right of collective bargaining and action’. Recently consolidated by a series of European Directives and Programmes, social solidarity is firmly established as the ‘fourth pillar’, completing the architecture of ‘indivisible’ values of peace, justice and freedom that constitutes the vision for European integration. Yet, as the UK's decision to opt out of the Solidarity Chapter illustrates, the legitimation of the principle of social solidarity at EU level is located within a polity that is dominated by tensions between closed national and open transnational politico-legal systems and arrangements. Despite this, the historical development of the European polity, civil and public spheres within and across nation-states has been characterised by a philosophical, political and social commitment to institutionalised forms of social solidarity (Esping-Anderson, 1990; Gallie and Paugam, 2000; Stjerno, 2005; Mau and Burkhardt, 2009). Underpinned by the philosophical traditions of the European Enlightenment, political and ideological struggles have forged national welfare regimes promoting collective institutionalised social solidarity while culturally embedding values of social and economic justice within public discourse (Maitre et al, 2005; Mau and Burkhardt, 2009). The social contract between the state and the individual has rested upon guaranteed protection from risks connected with the market economy that, in return, requires active participation in the labour market: ‘A lived daily experience of people sharing risks and responsibilities’ (Gray, 1999), where fiscal redistributive mechanisms and welfare services and benefits compensate people for the ‘worst dis-welfares of capitalism’ while giving citizens the opportunity to contribute to the national economic, social, and civil realm (Gough, 1979).