By using a unique combination of survey data (International Social Survey Program 2003) and qualitative case study, this dissertation investigates how much importance individuals and states place on descent (or ethnic identity) as a determinant of national membership. Through multi-level analysis across 29 twenty-nine countries, the first part of the dissertation (Chapter 2) shows that the negative effects of income and education on nativism are stronger in countries with greater levels of group threat (i.e., a higher percentage of foreign-born) and greater skill abundance (i.e., a higher percentage of college graduates and high GDP per capita). In contrast with the general pattern, higher income leads to stronger nativist attitudes in countries with low GDP per capita or a low percentage of foreign-born. To further investigate this reversed pattern, particularly in countries with a low percentage of foreign-born, the second part of the dissertation turns to a qualitative case study of selective dual citizenship policy in South Korea. In Chapter 3, the Korean dual citizenship policy is not merely a coethnic policy but a comprehensive tool to administer human resources, ranging from resident (dual) citizens to overseas diaspora and non-Korean migrants, to tackle demographic challenges and fulfill material and symbolic state interests. Economic and geopolitical interests have led to the preferential treatment of Korean Americans over Koreans in China. Dual citizenship was also extended to groups with less visible economic utility (e.g., return migrants over 65 and marriage migrants) to strengthen ethnic national identity and boost fertility. Chapter 4 shows that the Korean state uses dual citizenship to regulate resident and non-resident citizens regarding their choices in family formation, citizenship, and military service. In addition to draft evasion by dual citizens from elite backgrounds, non-resident (dual) citizens’ access to social welfare benefits has raised new tensions, inviting the public to question the definition of citizenship and the rights and obligations tied to citizenship. This study offers new insights into the field of citizenship studies by constructing a holistic approach to dual citizenship as part of a larger citizenship and immigration system to manage human resources, and by drawing attention to the rise of extraterritorial citizenship.