This article probes the consequences of basing post–World War I citizenship regimes on the Habsburg imperial network system for the control of mobility, a system known among specialists as Heimatrecht or pertinency. To date most of the historiography has focused on what this meant for national minorities in nationalizing states, with the most important studies thus far looking at the experience of Jews in Austria and Poland. We argue that though the national exclusionary tools of postwar pertinency are of undoubted importance, a larger, social trauma was experienced through post-Habsburg Europe, one that affected far more people and left many facing the consequences of potential statelessness. This article focuses on how postwar pertinency affected the worlds of work, welfare, and expulsion in the immigrant-rich industrial port town of Fiume, Europe’s smallest postwar successor state.