The Belgian Prosecutorial Strategy in Foreign Terrorist Fighters Cases and the Emergence of European Joint Investigation Teams: Moving Beyond Participation-Based Terrorist Liability?

The prosecution of Belgian foreign terrorist fighters linked to the Syrian-Iraqi conflict illustrates how evidentiary constraints can shape the development of counterterrorism criminal liability. Faced with persistent difficulties in proving terrorist offences and international crimes committed abroad, Belgian judicial authorities relied on the offence of participation in the activities of a terrorist group. Belgian courts progressively adopted an interpretation of terrorist participation encompassing organisational, logistical and ideological forms of support. The development of European Joint Investigation Teams, battlefield evidence-sharing practices and cooperation through Eurojust and Europol strengthened the capacity of national authorities to investigate conduct committed in Syria and Iraq. These developments facilitated prosecutions extending beyond participation-based terrorist liability towards more serious terrorist offences and, in certain cases, genocide, crimes against humanity and war crimes. The Belgian experience demonstrates how enhanced EU and International judicial cooperation may contribute to overcoming evidentiary constraints that favoured participation-based prosecutions in foreign terrorist fighter cases.