Citizenship of the European Union confers legal protection under a charter.
 Citizenship status, under social contract theory, carries with it both rights and duties
 Many countries (United Kingdom, Germany, United States, Canada) allow citizenship by marriage only if the foreign spouse is a permanent resident of the country in which citizenship is sought; others (Switzerland, Luxembourg) allow foreign spouses of expatriate citizens to obtain citizenship after a certain period of marriage, and sometimes also subject to language skills and proof of cultural integration (e

