33. Citizenship is in the competence of the State and should be based on a genuine link of the individual to the State. Nevertheless, contemporary developments set clear and increasing limits to States’ discretion in formulating policies regarding access to and stripping of citizenship, including prohibiting discrimination when conferring citizenship. Because it has a direct link to sovereignty, conferring citizenship falls, in principle, under the exclusive domestic jurisdiction of each individual State.74 States have a wide margin of appreciation in determining the criteria for granting citizenship, although this margin is not unlimited. First, the conferral of citizenship should be based on the existence of a genuine link between the State and the individual upon whom it is conferred, as expressed by the International Court of Justice.75 Second, even though States have the right to determine who their citizens are, they should not abuse this right by violating the principles of sovereignty and friendly, including good neighbourly, relations.76 Third, non-discrimination also applies to the area of citizenship, with the consequence that discretion in citizenship issues cannot amount to discrimination based on, inter alia, sex, religion, race, colour or national or ethnic origin.77 Discrimination includes differential treatment that directly or indirectly excludes specific groups of persons from access to citizenship due to their characteristics and does not pursue a legitimate aim or is not proportional to such an aim.78 There is a clear difference between discrimination and justified distinctions or preferential treatment in conferring citizenship.79 Justified distinctions may include, for example, a requirement that the applicant for citizenship possesses some knowledge of the State language in order to be naturalized or the facilitated acquisition of citizenship due to descent or place of birth. 74 75 76 77 78 79 The Hague Convention on Certain Questions relating to the Conflict of Nationality Laws, 1930; Council of Europe, European Convention on Nationality, 1997, article 3; and ETS no. 166, article 1. International Court of Justice, Nottebohm Case, 1955, ICJ 4. Also see Guideline 36. European Convention on Nationality, article 5(2). CERD, General Comment no. 11 on discrimination on the ground of citizenship, 1993, and CERD Geneva, Comment no. 30 on discrimination against non-citizens, 2004. Also see ECHR, Kuric´and others v Slovenia, application no. 26828/06, 2012. European Convention on Nationality. Guidelines on Integration of Diverse Societies 41