In 1992 the Treaty of Maastricht was adopted, that introduced inter alia a new concept: EU citizenship. It provided that EU citizens can rely on the rights ensured by the treaties and on free movement (Articles 20 and 21 TFEU). Since until that Treaty the provisions on free movement and non-discrimination on ground of nationality had been limited to workers and self-employed, this meant an important extension of rights. For workers, the Treaty guaranteed, already from the establishment of the EEC, that they had to be treated equally as national workers. Requiting equal treatment for economically non-active persons is much more problematic. If, for instance, anyone from the moment of entering a Member State would be entitled to social assistance, this might lead, it is feared, to ‘benefit tourism’ and that would clearly overstretch the solidarity of the host State. For this reason the combination of mobile EU citizens and social rights constitutes a politically highly sensitive area.