In cases against Russia and Azerbaijan, the Court has ruled that deprivation of nationality was disproportionate to the wrongdoing alleged and that the national security grounds were not made out.88 In cases that do not relate to national security, the CJEU has developed a somewhat stronger—though inconsistent—line of thinking on due process. In Rottmann,89 Tjebbes,90 JY91 and X,92 the Court has established rules on proportionality and the need for case-by-case consideration of cases (rather than providing for automatic loss in some circumstances) that also reflect the broader principles under the ECHR; although it has also found that withdrawal of nationality on grounds of fraudulent acquisition could sometimes be justified even if the person were rendered stateless.93 In a case against Argentina concerning nullification of naturalisation on grounds of fraud, the IACtHR set out detailed protections required for deprivation to be permissible—including proportionality, non-discrimination, prevention of statelessness, respect for due process and regard for the best interests of the child—though it found the conditions satisfied in the specific case.94 A due process argument has also succeeded in litigation at the national level in a number of African States challenging a continued prohibition or restriction on dual nationality that results in automatic loss for those who acquire or retain another (without permission).95 In sum, both national and international courts are, unsurprisingly, hesitant to challenge executive power in the highly politicised domain of national security; but they have been prepared to insist on minimum due process requirements and to take steps for the protection of children. 2.3. Arbitrary denial of nationality as arbitrary deprivation Media and scholarly attention to the litigation challenging deprivation of nationality has mainly focused on the expanded invocation of formal deprivation provisions in national law. More significant, however, may be the contribution of the regional human rights systems in expanding the scope of the prohibition of arbitrary deprivation: both to the cancellation or confiscation of identity documents on the grounds that they were issued in error, 96 and to the arbitrary denial of nationality to those apparently entitled in law.97 App Nos 52273/16, 52285/16, 52290/16, 52294/16 and 52302/16 (ECtHR, 25 June 2020); Ramadan v Malta App No 76136/12 (ECtHR, 21 June 2016). Case summaries in ECtHR, ‘Factsheet–Deprivation of Citizenship’ (November 2023). 88 Usmanov v Russia App No 43936/18 (2021) 72 EHRR 33; Emin Huseynov v Azerbaijan (No 2) App No 1/2016 (ECtHR, 13 July 2023). 89 Case C-135/08 Janko Rottmann v Freistaat of Bayern ECLI:EU:C:2010:104. 90 Case C-221/17 MG Tjebbes and Others v Minister van Buitenlandse Zaken ECLI:EU:C:2019:189. 91 Case C-118/20 JY v Wiener Landesregierung ECLI:EU:C:2022:34. 92 Case C-689/21 X v Udlændinge-og Integrationsministeriet ECLI:EU:C:2023:626. 93 For a survey of the development of this jurisprudence, see G-R de Groot and NC Luk, ‘Twenty Years of CJEU Jurisprudence on Citizenship’ (2014) 15 GermanLJ 821; see also J Shaw, ‘Deprivation of Citizenship: Is there an Issue of EU Law?’ in A Macklin and R Bauböck (eds), The Return of Banishment: Do the New Denationalisation Policies Weaken Citizenship? (European University Institute 2015) 47; H van Eijken, ‘Tjebbes in Wonderland: On European Citizenship, Nationality and Fundamental Rights’ (2019) 15 EuConst 714; D Kochenov and D de Groot, ‘Helpful, Convoluted and Ignorant in Principle: EU Citizenship in the Hands of the Grand Chamber in JY’ (2022) 47 ELRev 699. 94 Habbal v Argentina (IACtHR, 2022) Ser C No 463, para 97. 95 B Manby, ‘Is Litigation in African States Establishing a Right to Dual Citizenship?’ (GLOBALCIT, 30 June 2023) <https://globalcit.eu/is-litigation-in-african-states-establishing-a-right-to-dual-citizenship/>. 96 G-R de Groot and P Wautelet, ‘Reflections on Quasi-Loss of Nationality in Comparative, International and European Perspective’ (Centre for European Policy Studies, 2014). 97 Discussed as at 2008 in van Waas (n 12) ch V.