Ruben studied Law in Leuven and Madrid (2004), and also holds a bachelor in Philosophy. After practising as a lawyer specialized in migration and asylum law in Antwerp for three years, he worked for the then Flemish Minorities Centre (now Kruispunt Migratie-Integratie) and later as a legal officer and policy coordinator at the Belgian Refugee Council (CBAR-BCHV) for more than six years.
He also was an independent consultant, i.a. as national expert for the Asylum Information Database (AIDA) of the European Council for Refugees and Exiles (ECRE), and at the UN Refugees Agency (UNHCR) in Brussels on the issue of migration detention. In 2017 he coordinated the (start-up non-profit) organisation NANSEN, in combination with the teaching assistant position in Migration Law at the Ghent University with professor Desmet.