During the ‘long eighteenth century’, several thousands of sailors born outside British territories served in the Royal Navy. This phenomenon, and the peculiarities of their employment compared to that of British seamen, remain largely unstudied. This paper aims to show that, as far as disabilities or privileges were concerned, official legislation only played a very small part in making alien seamen's experiences in the navy distinct from those of their British colleagues. More broadly, this article argues that, whilst transnationalism can be overemphasized, there are specific contexts and groups of people for which the power of the state falters when it comes to obstructing movement, and indeed it is forced, for its very survival, to act strategically against the barrier to circulation that frontiers normally constitute. In similar circumstances, the origins of the individuals concerned, intended as official labels that states normally use to classify them, control them, and claim or disclaim ownership over them, can become all but meaningless. Thus, naval sailors, as useful state servants, can be an excellent case-study to understand the category of legal ‘foreignness’ as it developed in modern nation-states, and the tensions inherent to it.