Biometric Technology at the Borders of Citizenship 315 case: States tend to keep their borders virtually unaltered for decades – when not centuries; meanwhile, satellite surveillance, physical fences, urban control, air and water patrolling, remote sensing, shared identity repositories, and especially the globe-wide deployment of biometric tracking are redefining the landscape of who can move and where to. To be sure, the extensive deployment of biometric tracking at States’ borders has been with us for almost two centuries already (Breckenridge 2014), but with the caveats that it was not operable remotely and it was neither digital, nor algorithmic: it is automation and remote operability that makes biometrics nearly inescapable today. Blind spots are becoming increasingly rare, and those who embark onto exploiting these residual fault lines in search of a more dignifying future are often criminalised and incarcerated as biopolitical waste (Corcodel and Fragkou 2023; Lesutis and Kaika 2024). This bears evident repercussions on the meaning of citizenship and the multi-layered fragmentation of our rather fragile planet based on transnational wealth-sorted classes and new migratory élites (Vecellio Segate 2022c; Walsh 2014). Because the administration and recording of individuals’ identities, under the comfortable rhetorical tenet of their “protection”, is central to the very existence of a population and thus of a State itself, public international law (PIL) – as the legal regime applicable between sovereign States – has long been concerned with the question of citizenship and the bureaucratic control thereof (Chakrabarty 2021; Soomro 2023). Within this extremely broad landscape, issues of “borderline citizenship” such as statelessness, nomadism, displacement, and refuge have gained momentum as a core concern for public international lawyers, due to both their transnational nature (in most cases at least) and their inevitable interfaces with the human-rights and human-security agendas. In particular, recent scholarship (e.g. Jain 2022) has brilliantly unpacked the State as a proactive producer of borderline citizenship as opposed to a discourse traditionally focused on the State as a “humanitarian” agent whose interest would rest with closing such gaps. Public international lawyers are all the more concerned as the current post-Westphalian configuration of international relations displays the properties of a regulatorily captured regime which is fraught with exclusionary exceptionalisms, carveouts, and grey areas, where transnational capital flows thrive along with their reference élites (Buzan and Little 1999; Grell-Brisk 2018), but specific classes of “faceless” individuals often remain trapped in-between domestic laws, to no one State’s avail (Benhabib 2020). It seems appropriate to clarify from the outset that references here will be to citizenship and not to nationality: the two terms are too often confused, but the former strictly refers to the objective legal status of being recognised as a “citizen” by a State, while the latter broadly describes a sense of self-assessed ethno-cultural affiliation, bond, kinship, and belonging to a national community (von Rütte 2022, 11–57). This is not to say that nationality is completely alienated from entitlements