The threat represented by foreign fighters to their home state has rarely materialised, yet states have increasingly legislated against foreign fighters over the course of the last 300 years. This observation points to the act of legislating as fulfilling some function other than the protection of the state against a physical threat presented by foreign fighter returnees. This paper asks what is problematic about foreign-fighter returnees from the point of view of lawmakers if they do not represent a physical threat? It argues that returnees generate ontological insecurity on the part of lawmakers. Consequently, the act of legislating against them serves to reify the identity of individual lawmakers. This argument is supported using historical case comparison of Westminster parliamentary debates on foreign fighting. This paper finds that what is at stake in foreign-fighter legislation is not the physical security of the national state but the ontological security of lawmakers. These findings point to the need for a shift of the research on foreign fighters that moves beyond the potential terrorist threat they represent to an understanding of what they mean for International Relations.