Meijers Committee standing committee of experts on international immigration, refugee and criminal law naturalised citizens it can be applied to children of immigrants who acquired the nationality at birth and lived in the country ever since. Generally, they will have a closer link with the country than naturalised citizens. At the national level, the French Conseil Constitutionnel considered in 2005 that the distinction between naturalised and born citizens was constitutional. In reaching this conclusion, it took into consideration that the distinction did not apply to persons having held French nationality for more than 10 years. After the extension of this period to 15 years, in 2006, the Conseil again found the legislation to be in accordance with the constitution but stipulated that a longer period would make its constitutionality doubtful. According to the German Bundesverfassungsgericht, loss of nationality should be ‘zeitnah’, not too long after acquisition, in order to avoid conditional citizenship.103 Constitutional practice in both countries thus suggests that, where a ground for citizenship deprivation applies only to naturalised citizens, the applicability of that ground ought to be limited in time. In the same vein, the UN Secretary-General has pointed out that temporal limitations to citizenship deprivation mitigate the vulnerability of naturalised citizens to loss or deprivation of citizenship.104 At the European level, there exists little room for distinctions between citizens by birth and those who obtained their citizenship through naturalisation. Article 5(2) ECN provides that the State Parties ‘shall be guided by the principle of non-discrimination between its nationals, whether they are nationals by birth or have acquired its nationality subsequently’. In the case of Biao v. Denmark, the ECtHR Grand Chamber had to decide on Danish immigration rules that restricted family reunification for persons who had been Danish citizens for less than 28 years. The Grand Chamber established that this ’28 year rule’ was likely to disadvantage Danish citizens who had received their Danish nationality through naturalisation and who, moreover, ‘would generally be of foreign ethnic origin’.105 The Grand Chamber concluded that the Danish legislation amounted to indirect differential treatment on the ground of ethnic origin, which requires very weighty reasons in order to be justified (see further in the next paragraph).106 In the same judgment the Grand Chamber noted that Article 5(2) ECN must be seen as evidence of a trend towards a European standard of non-discrimination between citizens by birth and citizens by naturalisation.107 It is noteworthy that none of the four State Parties that differentiate between born and naturalised citizens (BE, FR, IT and UK) have ratified the ECN, France and Italy have only signed. 103 Bundesverfassungsgericht 24 May 2006, 2 BvR 669/04, BVerfGe 116, 24-69, paras 72 and 76; Tabbara 2019 and Kiessling 2015, p. 1-34. 104 Report of the UN Secretary-General on Human rights and arbitrary deprivation of nationality of 19 December 2013, UN Doc. A/HRC/25/28 (2013), para 6. 105 Biao/Denmark, para 112. 106 Biao/Denmark, para 114. 107 Biao/Dnemark, para 132. 21