This article will analyse the use of genealogy in the context of race, place, and justice via the concepts of nationality/citizenship and cultural/national identity, including “imagined communities”. Analysis is undertaken through the legal concept of “jus sanguinis” and simultaneous differing interpretations of “citizen”, including the concept of “effective nationality”. The latter incorporates the Nottebohm principle “shared sentiments and interests” and is particularly relevant in “security situations. This article argues that “effective nationality” is indicative of the Anderson’s famous landmark study of nationalism, “Imagined Communities”. The legal concept of jus sanguinis draws upon genealogy: “A line of descent traced continuously from an ancestor”. However, the imagined communities to which someone perceives they belong, through ancestral lineage, or cultural, political or religious affinity are often highly contested cultural notions, not least in times of political unrest. This article will focus on the UK and show how liberal policies and criteria initially aimed at the expansion of citizenship have, in the 21st century, similarly enabled exclusion. However, I argue that the current exclusion process is the simultaneous use of jus sanguinis and cultural interpretations of “effective nationality” when applied to those who supported proscribed groups, for example ISIS in Syria. This paper uses legislation, media comment, and the legal case studies of Nottebohm and Shamima Begum.