Since the Syrian conflict began in 2011, thousands of EU nationals have travelled or attempted to travel in conflict zones in Iraq and Syria to join insurgent terrorist groups, such as ISIL/Da’esh (‘Islamic State’). Of those, it has been estimated that around 30 % have already returned to their home countries. The issue of foreign fighters has been high on the political agenda at both Member State and EU level for the last five years and touches upon a wide range of policies: policies related to the prevention of radicalisation; to information exchange at EU level; to criminal justice responses to returnees; to disengagement/deradicalisation inside and outside prisons. This study aims at outlining the EU response to the issue of returning foreign fighters and their families. It furthermore examines how six Member States have responded to this phenomenon so far (Belgium, Denmark, Germany, France, the Netherlands and the UK). These Member States are confronted with significant challenges in dealing with foreign fighters that combine legal, ethical and practical questions regarding their obligations and capabilities as regards the handling of the foreign fighters still abroad and the returnees already on EU soil. Meanwhile, Member States’ existing programmes aiming at tackling radicalisation are difficult to evaluate, leading to uncertainties as regards the efficiency of current practices.