Free movement of persons, the right to welfare across borders and equal treatment constitute a core part of a European social Union. Together these three principles constitute the nexus of Union solidarity. Over the last decades, the scope and limits of the emerging social Union has been defined and contested. The Union legislatures and the Court of Justice of the European Union (CJEU) have decided and interpreted rights and obligations. Implementation hereof, however, is carried out by the Member States. In this paper, we examine how the right to social assistance for economically inactive European citizens is implemented on the ground. We analyse the implementation of complex Union rules and show how the meaning and scope of a European social Union is disputed on the ground. Firstly, limited legal guidelines across local and national executive levels prevent local front-desk officials from having the required information on the legal framework. Secondly, national and local executive levels exploit the legal uncertainty called forth by the complex EU rules and jurisprudence, opting for restrained access to social assistance. Our findings demonstrate that the European social Union is highly contested on the ground and mainly eligible for those who can protect themselves.