This project seeks to compare and classify laws determining full membership status in various states, identifying bases underlying the different regimes such as family unity, service, ethnic and racial identity, linguistic and social commonality, religious and political ideology, and duration of residence. Residence over time, for example, often leads to lawful long-term residence or citizenship, a time-makes-right concept also reflected in other areas of the law, such as prescriptive property rights, common law marriage, de facto parentage, and statutes of limitation.
This project also seeks to identify patterns in legal development over time. For instance, states with expanding territory or influence often liberalize their birthright citizenship rules to legitimize colonial or ideological claims on others. Post-colonial powers, in contrast, may restrict immigration and citizenship to focus inward, conserving privilege and the perceived common identity among citizens.