Urban growth and the unprecedented expansion of imperial Spain sparked a sense of constant fluctuation and anonymity that challenged early modern categories of belonging and space demarcation. The Spanish crown claimed a monopoly which sought to exclude tentatively defined foreigners, and in the peninsula, urban growth encouraged measures to identify and restrict the presence of the 'undeserving' poor. Nascent frameworks of legal identity exacerbated a public discourse of suspicion against constant motion and the 'undocumented', and this interaction between mobility and emerging techniques of identification has an intellectual history that has not received sufficient attention. The Dominican theologian Francisco de Vitoria controversially oscillated between the ethical defence of hospitable behaviour and a notion of 'openess' permeated by the language of the rights of 'nations'. His disciple Domingo de Soto more openly challenged current measures by insisting on the limits of any attempt to create fixed definitions of poverty and legitimate movement. This research explores how movement was both monitored and discussed in a highly mobile world of fragile categories of identity and fragmentary and porous boundaries. It inquires how different narratives of identity and belonging were articulated in regulations and legal cases, and examines their influence on intellectual debates about hospitality and kindness to strangers in both transatlantic and local frameworks. In this context, I intend to offer new insights on the means through which nebulous identities and mechanisms of identification were incorporated to an emerging bureaucracy of movement, and contribute to a better understanding of how these practices helped shape the terms in which freedom of movement was advocated or objected. This research claims that the discursive ambivalence of notions like the right to travel or the itinerant-undeserving poor, exposed a climate of resistance to an emerging bureaucracy of identification and increasing mobility regulations.