Opinion of the Advocate General — ECLI:EU:C:2023:999
Date: 2023-12-14
Language of the case: German
Subject matter: Citizenship of the Union
Procedure: Reference for a preliminary ruling
Origin: Germany

summary of the legal framework, of Article 7(1)(a) of the European Convention on Nationality, (36) what public interest ground or grounds are pursued by Paragraph 25(1) of the StAG. However, given that that provision can only be compliant with EU law if it pursues a legitimate public interest ground, it should be examined in the light of the observations of the German government. 48. As the city of Krefeld and the German Government have indicated, and as is apparent from the statement of reasons for the Law reforming the law on nationality of 15 July 1999, Paragraph 25 of the StAG is intended, inter alia, to prevent multiple nationality. (37) The German Government states, in addition, that the case-law of the Bundesverfassungsgericht (Federal Constitutional Court, Germany) holds that the legislature’s decision to obstruct unlimited multiplicity of nationalities is beyond criticism. (38) 49. In that regard, there is no doubt that a system such as that provided for by Paragraph 25 of the StAG falls within the exercise of the power of the Member States to define the conditions of acquisition and loss of nationality and that, in exercise of that power, it is legitimate for a Member State, such as the Federal Republic of Germany, to take the view that the consequences of holding multiple nationalities should be avoided in certain cases. (39) 50. The legitimacy, in principle, of that objective is corroborated by Article 7(1)(a) of the European Convention on Nationality, under which a State Party may not provide in its internal law for the loss of its nationality ex lege or at the initiative of the State Party except, inter alia, in the case of voluntary acquisition of another nationality. (40) According to the explanatory report on that convention, whether persons who voluntarily acquire another nationality are allowed to retain their previous nationality will depend upon the individual situation in each State. (41) 51. I would observe, in that regard, that EU law does not preclude a Member State from providing for the issue of whether or not there is a genuine link with that State to be assessed by applying a test, such as that set out in Paragraph 25(1) of the StAG, based on voluntary acquisition of the nationality of a third country by the person concerned; nor, against a legislative background in which multiple nationality is, in principle, to be avoided, does it preclude that Member State from requiring the person concerned to follow a specific procedure, such as that set out in Paragraph 25(2) of the StAG, where he or she wishes to retain German nationality. 52. In those circumstances, I consider, like the German and Estonian Governments and the Commission, that, in the circumstances of the main proceedings, EU law does not, in principle, preclude a Member State, in the situations contemplated by Paragraph 25 of the StAG, from providing, on public interest grounds, for automatic loss of nationality where its nationals voluntarily acquire the nationality of a third country, even where that loss entails, for the person concerned, the loss of his or her EU citizenship. 53. That having been said, in order for national legislation such as that at issue in the main proceedings, which provides for the loss of EU citizenship, to be compliant with EU law, it must not only seek to pursue legitimate public interest grounds, but also comply with the principle of proportionality. 2. Review of the proportionality of the consequences arising from the loss of nationality from the point of view of EU law 54. While, as I have just set out, EU law does not, in principle, preclude the legislation at issue in the main proceedings, I would nevertheless observe that it is apparent from settled case-law that, having regard to the importance which primary EU law attaches to the status of citizen of the European Union, which constitutes the fundamental status of nationals of the Member States, the competent national authorities and national courts must determine whether the loss of the nationality of the Member State concerned, when it entails the loss of citizenship of the European Union and the rights attaching thereto, has due regard to the principle of proportionality so far as concerns the consequences of that loss for the situation of the person concerned and, if relevant, for that of the members of his or her family, from the point of view of EU law. (42) 55. Furthermore, it is apparent from the same case-law that the loss of the nationality of a Member State by operation of law would be inconsistent with the principle of proportionality if the relevant national rules did not permit at any time an individual examination of the consequences of that loss for the persons concerned from the point of view of EU law. (43) 56. In the present case, I would observe that, in accordance with Paragraph 25(2) of the StAG, German nationals wishing to acquire, voluntarily, the nationality of a third country may make an application to retain their German nationality under the advance permission procedure which provides that, in the decision on an application for permission, the public and private interests are to be weighed up. 57. The question arises, as a preliminary matter, of whether the examination of proportionality required by EU law can be conducted by the competent authorities only at a specific point in time – namely, in this case, before the automatic loss of nationality and thus of EU citizenship, within the framework of the advance permission procedure. 58. That is not a difficult question to answer. In the light of the case-law referred to in point 55 of this Opinion, it is, in principle, possible for a Member State, such as the Federal Republic of Germany, to provide that the examination of proportionality is to be conducted within the specific framework of an advance permission procedure, such as that provided for by Paragraph 25(2) of the StAG. However, as is apparent from that same case-law, in order to be compatible with EU law, that provision must guarantee the right to an individual examination of the proportionality of the consequences, for the persons concerned and, if relevant, for the members of their family, of the loss of German nationality, from the point of view of EU law. 59. The referring court is not sure that that requirement is met in the present case. I confess that I also find it difficult to understand how that procedure relates to the principle of proportionality and, more specifically, how its application guarantees the right to an individual examination required by EU law. Accordingly, in what follows I will analyse, first, the procedural arrangements provided for by Paragraph 25(2) of the StAG and, secondly, the substantive scope of the examination of proportionality for which it provides. (a) The procedural arrangements provided for by Paragraph 25(2) of the StAG 60. It will be recalled that, under Paragraph 25(2) of the StAG, German nationality can be retained if, prior to acquiring the nationality of a third country, the person concerned has obtained, from the competent authority, written permission to retain his or her nationality. 61. The question therefore arises of whether, within the framework of the advance permission procedure, the time limits within which the application must be made – and the permission obtained – are compatible with EU law. If they are to be compatible, those time limits must not prevent the persons concerned from exercising the rights attaching to their EU citizenship in an effective manner. 62. With regard, in the first place, to the time limit applicable to the making of the application for permission, the Court has held that the Member States may require, on the basis of the principle of legal certainty, that an application for the maintenance or recovery of nationality be submitted to the competent authorities within a reasonable period. (44) 63. It follows, in my opinion, that a requirement for an application for permission to retain the nationality of a Member State to be made before the acquisition of the nationality of a third country, as imposed by Paragraph 25(2) of the StAG, appears to meet the criterion of a reasonable period within the meaning of that case-law, provided that, in principle, it does not prevent the nationals concerned from exercising their right to an individual examination by the competent authorities of the proportionality of the consequences of the loss of nationality, from the point of view of EU law. 64. That having been said, I should point out that it is apparent on reading the orders for reference, the observations of the applicants in the main proceedings relating to case C‑686/22, and the observations of the Commission, that there is uncertainty as to whether the applicants in the main proceedings were duly informed of the consequences of recovering Turkish nationality on their situation and that of their families in the specific legislative context of the reform of the RuStAG. 65. The applicants in the main proceedings state that, when they made their application to recover Turkish nationality, the legislation that was in force permitted them to recover that nationality. There was therefore no reason to make the application for advance permission. They also state that the change in the law was not clearly explained or brought to their attention. It was after they had made their application to recover Turkish nationality that the RuStAG was amended and the possibility for German nationals resident in national territory to obtain dual nationality was withdrawn and limited. I have some remarks to make about those observations. 66. On the one hand, in the light of the case-law, (45) it seems at least plausible, having regard to the dates on which Turkish nationality was recovered, as indicated by the referring court, under the system instituted by Paragraph 25 of the StAG, that the applicants in the main proceedings did not have effective access to an individual examination of their situation from the point of view of EU law. 67. As the Commission has rightly stated, it must be borne in mind that, first, the law in force up to 31 December 1999 neither required nor, where applicable, permitted an application to be made to retain German nationality in the event of Turkish nationality being recovered by a German national resident in national territory. Secondly, as the referring court has also pointed out, during the period between the entry into force of the amended version, on 1 January 2000, and the recovery of Turkish nationality, no possibility of initiating and effectively conducting such a procedure was open to, inter alia, persons who had recovered Turkish nationality in early 2000, such as the applicants. (46) Thus, some of the persons concerned were deprived, prior to the loss of German nationality, of the possibility of effective access to the examination of their individual situation required by EU law, this being a matter for the referring court to verify. (47) 68. On the other hand, in the light of that same case-law, it is possible in my opinion, having regard to the serious consequences of losing the nationality of a Member State, to require of national authorities and courts that the persons concerned must be duly informed, first, of the fact that if they were to acquire or recover the nationality of a third country, that would entail the loss of German nationality, and, secondly, of the advance permission procedure which enables an application to retain that nationality to be made, and of the time limit for making such an application. 69. In the present case, it is for the referring court to determine, amongst other things, having regard to the fact that the applicants in the main proceedings were required to renounce their Turkish nationality in order to acquire German nationality during a period of legislative change, whether they can be considered to have been duly informed. (48) 70. With regard, in the second place, to the time limit for obtaining permission to retain German nationality, laid down in Paragraph 25(2) of the StAG, I must observe that, under that provision, the moment when the nationality of a third country is obtained marks the expiry of the time limit not only for making the application to retain German nationality, but also for obtaining such permission. Consequently, if such an application for permission is yet to be processed by the competent German authorities on the date when the authorities of the third country issue their decision, it can no longer be examined, which entails the loss of EU citizenship without the persons concerned having had the possibility of effective access to the examination of proportionality required by EU law. The loss of EU citizenship depends, in practice, on a number of factors such as how quickly the competent German authorities conduct the weighing-up of public and private interests and how quickly the application for acquisition of nationality is processed by the authorities of the third country. That having been said, I must point out that the provision at issue does not require the person concerned to make an application to acquire the nationality of a third country at the same time as making an application for permission to retain German nationality. Consequently, in principle, the problem should not arise in so far as the person concerned ought to wait for the German authorities’ decision on permission to retain nationality before making an application to acquire the nationality of a third country. 71. Furthermore, in so far as the applicants in the main proceedings thought they could retain both German and Turkish nationality, as German nationals resident in Germany were permitted to do under Paragraph 25 of the RuStAG (which was applicable until 31 December 1999), I share the Commission’s view that it would have been ‘appropriate’ to enact transitional provisions to that effect. Such transitional provisions would have enabled persons who had made their application to recover Turkish nationality under the law in force prior to 1 January 2000, but who obtained Turkish nationality after that date, to make effective use of the advance permission procedure provided for by Paragraph 25 StAG. Having regard to the serious consequences that the loss of EU citizenship has for the persons concerned, the lack of any such transitional provisions is, in my view, incompatible with the principle of effectiveness. 72. Accordingly, having regard to the serious consequences of losing German nationality and, with it, the status of the applicants in the main proceedings as citizens of the European Union, both the application in the present case of the procedural arrangements, such as the time limits laid down by Paragraph 25(2) of the StAG, and the lack of any such transitional provisions seem to me to be incompatible with the principle of effectiveness, in so far as those arrangements or their absence fetter the applicants’ right to obtain an examination of proportionality. (b) The substantive scope of the individual examination provided for by Paragraph 25(2) of the StAG 73. Contrary to what is stated by the city of Krefeld and the German Government, the referring court states that in practice, despite the wording of Paragraph 25(2) of the StAG, where an application for advance permission to retain German nationality is rejected by the competent authorities, no individual examination of the proportionality of the consequences of losing German nationality, from the point of view of EU law, is carried out either by those authorities or by the national courts. 74. In the first place, I would observe that if, after the referring court has carried out the necessary verifications, that proves to be the case, the mere fact that such an examination is a formal or theoretical part of the advance permission procedure is not sufficient – if, in practice, the examination is not carried out – to ensure that that procedure is compatible with Article 20 TFEU. In that case, it is apparent from settled case-law of the Court (49) that the referring court must be in a position to require the national authorities to carry out that examination or to examine for itself the consequences of the loss of German nationality for the persons concerned and, where appropriate, to have them recover that nationality ex tunc. (50) 75. That having been said, the German Government submits, in that regard, that Paragraph 25(2) of the StAG enables a full examination of the legal situation of the person concerned to be made and that the fact that regard is had not only to the public interest in German nationality being retained, but also to the private interest, necessarily means that the interest in retaining EU citizenship is taken into account. If the referring court were to consider that the competent national authorities do conduct the individual examination of the consequences of loss of EU citizenship required by EU law, as indicated by the German Government, it would also have to establish the date from which such examinations have been carried out. If it were to find that such examinations have only been carried out since the date of delivery of the judgment in Tjebbes and Others, I must reiterate that any person who lost German nationality by operation of law prior to that date, under Paragraph 25(1) of the StAG, must be able to obtain such an examination and, where appropriate, recover German nationality ex tunc in the context of an application for a travel document or any other document showing his or her nationality, and more generally, in the context of proceedings for a declaration of nationality. (51) 76. In the second place, it is apparent from the orders for reference that the applicants in the main proceedings have built a family and professional life in Germany. As German nationals, they were able to exercise their freedom of movement and residence in other Member States. 77. In that regard, I would point out at the outset that, within the scope of application of EU law, every EU citizen is guaranteed the same level of protection of his or her fundamental freedoms, in particular, his or her right to a family life. 78. In particular, as regards that right, it is apparent from well-established case-law that, first, the examination of proportionality must include an individual assessment of the situation of the person concerned and that of his or her family in order to determine whether the consequences of losing the nationality of the Member State concerned, when it entails the loss of his or her citizenship of the European Union, might, with regard to the objective pursued by the national legislature, disproportionately affect the normal development of his or her family and professional life from the point of view of EU law. (52) Secondly, as part of that examination of proportionality, it is, in particular, for the competent national authorities and, where appropriate, for the national courts to ensure that the loss of nationality is consistent with the fundamental rights guaranteed by the Charter, the observance of which the Court ensures, and specifically the right to respect for family life as stated in Article 7 of the Charter. Furthermore, that article must be read, where applicable, in conjunction with the obligation to take into consideration the child’s best interests, recognised in Article 24(2) of the Charter. (53) 79. In the third place, a question which is important to the outcome of the disputes in the main proceedings arises at this stage: what is the relevant date to be taken into account by the competent authorities for the purposes of the examination of proportionality? It could be argued that, as the Court held in the judgment in Udlændinge- og Integrationsministeriet, that date corresponds to the day on which the person concerned obtained or recovered the nationality of a third country, since, in the present case, in accordance with Paragraph 25(2) of the StAG, that date forms an integral part of the legitimate criteria which that Member State has determined, and on which the retention or loss of nationality depends. 80. It is quite certain however that, in contrast to the situation in the case which gave rise to the judgment in Udlændinge- og Integrationsministeriet, (54) in the present case, the answer to that question cannot stop there and must take account of an important factor, namely that the applicants in the main proceedings were not in any circumstances in a position to initiate the procedure for advance permission to retain their German nationality, as Paragraph 25(2) of the StAG had not yet entered into force on the date when they made their applications to recover Turkish nationality. It was thus impossible – both procedurally and substantively – for the applicants in the main proceedings to make an application for advance permission. Since a time limit for applying to retain German nationality had yet to be prescribed, it could not expire, the result being that the persons concerned did not have effective access to an individual examination of their situation from the point of view of EU law. (55) 81. In the fourth place, and lastly, it seems to me that there is one more factor which must be considered. I note that the referring court states that German law makes no provision for an ancillary examination of the consequences of loss of German nationality after it has been lost. In such circumstances, the only way for the persons concerned to recover German nationality – without retroactive effect – would be to make another application for naturalisation. (56) 82. That possibility of recovering nationality, given that it entails that the person concerned is deprived, for a certain period, of the possibility of enjoying all the rights conferred by citizenship of the European Union, without it being possible for those rights to be restored during that period, is not compatible with the well-established case-law of the Court. According to that case-law, the fact that national law does not offer the possibility, under conditions which are consistent with EU law, to obtain from the national authorities and, potentially, from the national courts, an examination of the proportionality of the consequences of the loss of the nationality of the Member State concerned from the point of view of EU law and which may, where appropriate, lead to the recovery ex tunc of that nationality, cannot be compensated for by the possibility of naturalisation, regardless of the conditions – possibly favourable – under which that naturalisation may be obtained. To accept that the position is otherwise would be tantamount to accepting that a person could be deprived, even for a limited period, of the possibility of enjoying all the rights conferred on him or her by virtue of his or her citizenship of the European Union, without it being possible for those rights to be restored for that period. (57) VI. Conclusions 83. In the light of the above considerations, I propose that the Court should answer the questions referred for a preliminary ruling by the Verwaltungsgericht Düsseldorf (Administrative Court, Düsseldorf, Germany) as follows: Article 20 TFEU, read in the light of Article 7 of the Charter of Fundamental Rights of the European Union, is to be interpreted as meaning that it does not preclude legislation of a Member State providing that its nationals, in the event of voluntary acquisition of the nationality of a third country, lose the nationality of that Member State by operation of law, which entails, for those who are not also nationals of another Member State, the loss of their EU citizenship and of the rights attaching thereto, unless they obtain permission to retain that nationality before acquiring the nationality of the third country, provided that the persons concerned have effective access, subject to a reasonable time limit, to a procedure for retaining nationality which enables the competent authorities to examine the proportionality of the consequences of the loss of that nationality from the point of view of EU law and, where appropriate, to allow that nationality to be retained or recovered ex tunc. Such a time limit cannot begin to run until those authorities have duly informed the persons concerned of the fact that the potential acquisition or recovery of the nationality of a third country entails the loss of nationality and of the possibility of initiating the advance permission procedure enabling an application to retain that nationality to be made, and also of their right to apply, subject to that time limit, for the retention or recovery of that nationality. Otherwise, those authorities must be in a position to conduct such an examination, as an ancillary matter, where an application is made, by those persons, for a travel document or any other document showing their nationality, or, where applicable, in proceedings for a declaration of the loss of nationality. 1 Original language: French. 2 Judgment of 2 March 2010 (C‑135/08, EU:C:2010:104; ‘the judgment in Rottmann’). 3 Judgment of 12 March 2019 (C‑221/17, EU:C:2019:189; ‘the judgment in Tjebbes and Others’). 4 Judgment of 18 January 2022 (C‑118/20, EU:C:2022:34; ‘the judgment in Wiener Landesregierung’). 5 Judgment of 5 September 2023 (C‑689/21, EU:C:2023:626; ‘the judgment in Udlændinge- og Integrationsministeriet’). 6 In its consolidated version (Bundesgesetzblatt III, No 102-1, as amended by Article 1(7), of the Gesetz zur Reform des Staatsangehörigkeitsrechts (Law reforming the law on nationality), of 15 July 1999 (BGBl. I p. 161). 7 Taken by the cities involved in the main proceedings relating to the three cases on 13 September 2019, 24 February 2021 and 12 February 2021, respectively. 8 Under Paragraph 30(1) of the StAG: ‘The nationality authority shall determine the existence or non-existence of German nationality upon application if there is credible evidence of a legitimate interest. The determination shall be binding in all matters for which the existence or non-existence of German nationality has legal relevance. Where there is a public interest, the determination may be made of the authority’s own motion.’ 9 BGBl., p. 583. 10 For the sake of completeness, I would state that academic writers explain that that reform of the RuStAG introduced elements of ius soli and made it easier for foreign nationals resident in Germany – and especially their children born in that Member State, to acquire German nationality. Those writers state that, since the legislation entered into force, amendments have been made in 2004, 2007, 2009, 2014 and 2019. See, in particular, Farahat, A. and Hailbronner, K., Report on Citizenship Law: Germany, RSCAS/GLOBALCIT-CR 2020/5, European University Institute, Country Report 2020/05, March 2020, p. 33. 11 The acquisition of German nationality thus occurred under the first sentence of Paragraph 25(1) of the RuStAG, which was in force until 31 December 1999 and contained the ‘Inlandsklausel’ (‘the domestic clause’) under which German nationality was lost only where the German national in question was ‘neither domiciled nor permanently resident in federal territory’. That clause was deleted in Paragraph 25 of StAG. The Commission refers in its observations to the statement of reasons for the draft law reforming the law on nationality of 15 July 1999 [German Bundestag document 14/533 of 16 March 1999, p. 15] which states that ‘this “domestic clause” is often used to circumvent the principle that multiple nationalities are to be avoided in naturalisation: the foreign nationality abandoned prior to naturalisation is reacquired, without penalty, after naturalisation. The abolition of the “domestic clause” eliminates the possibility of such abuse’. See, in that regard, in particular, McFadden, S.W., ‘German Citizenship Law and the Turkish diaspora’, German Law Journal, 2019, No 20, p. 72, especially pp. 74 to 78; Falcke, S., and Vink, M., ‘Closing a Backdoor to Dual Citizenship: The German Citizenship Law Reform of 2000 and the Abolishment of the “Domestic Clause”’, Frontiers in Sociology, 2020, Vol. 5, p. 1, especially pp. 3 to 5, and Bouche, N., ‘La réforme de 1999 du droit allemand de la nationalité’, Revue international de droit comparé, 2002, Vol. 54(4), p. 1035. 12 See point 18 of this Opinion. 13 C‑689/21, EU:C:2023:53. For the sake of brevity I refer, for a summary of that case-law, to points 29 to 43 of that Opinion. 14 See, to that effect, judgments in Rottmann, paragraph 45; Tjebbes and Others, paragraph 32; Wiener Landesregierung, paragraphs 37 and 51, and Udlændinge- og Integrationsministeriet, paragraph 30 and the case-law cited. It is a question of the application of a fundamental principle of EU law in the sphere of EU citizenship. See also, in that regard, the case-law cited in paragraph 41 of the judgment in Rottmann. 15 Judgment of 7 July 1992 (C‑369/90, EU:C:1992:295, paragraph 10). 16 Paragraphs 41, 42 and 45. 17 See Opinion of Advocate General Poiares Maduro in Rottmann (C‑135/08, EU:C:2009:588, points 23, 24 and 26). Thus, according to Advocate General Poiares Maduro, there is no question of inferring from that principle that it is absolutely impossible to deprive a person of nationality, where such deprivation would entail the loss of citizenship of the European Union, or of considering that the conditions for the acquisition and loss of nationality fall outside the jurisdiction of EU law. 18 Judgment in Rottmann, paragraph 41. 19 See, in that regard, judgments in Rottmann, paragraphs 39, 41 to 43, 45, 48, 56, 55 and 59; Tjebbes and Others, paragraphs 30, 32, 40 to 42 and 45, and Wiener Landesregierung, paragraphs 44, 59, 61 and 73. 20 Paragraphs 48, 55 and 56. 21 Judgments in Tjebbes and Others, paragraph 40; Wiener Landesregierung, paragraph 58, and Udlændinge- og Integrationsministeriet, paragraph 38. 22 Judgments in Rottmann, paragraphs 55 and 56; Tjebbes and Others, paragraph 41; Wiener Landesregierung, paragraph 59, and Udlændinge- og Integrationsministeriet, paragraph 39. 23 Judgments in Tjebbes and Others, paragraph 45; Wiener Landesregierung, paragraph 61, and Udlændinge- og Integrationsministeriet, paragraph 55. 24 Judgments in Tjebbes and Others, paragraph 42, and Udlændinge- og Integrationsministeriet, paragraph 40. 25 It may be recalled that the case giving rise to that judgment concerned the situation of a citizen who had been born in the United States of America to a Danish mother and an American father and who, from birth, had held both Danish and American nationality. After reaching 22 years of age, she applied to the Udlændinge- og Integrationsministeriet (Ministry of Immigration and Integration, Denmark) to retain her Danish nationality. By decision of the competent minister, she was informed that she had lost her Danish nationality upon reaching the age of 22 and that it was not possible to grant her application to retain her nationality because it had been made after she had reached that age. 26 Judgment in Udlændinge- og Integrationsministeriet, paragraph 40 and the case-law cited. 27 Judgment in Udlændinge- og Integrationsministeriet, paragraphs 41 and 43 and the case-law cited. 28 Judgment in Udlændinge- og Integrationsministeriet, paragraph 48 and the case-law cited. 29 See, in particular, judgments of 20 September 2001, Grzelczyk (C‑184/99, EU:C:2001:458, paragraph 31), and Udlændinge- og Integrationsministeriet, paragraph 29 and the case-law cited. 30 Article 20(2) TFEU, first subparagraph. 31 See points 28 to 31 of this Opinion. 32 Judgment in Udlændinge- og Integrationsministeriet, paragraph 30 and the case-law cited. 33 Judgment in Udlændinge- og Integrationsministeriet, paragraph 30 and the case-law cited. 34 Judgments in Rottmann, paragraph 51; Tjebbes and Others, paragraph 33; Wiener Landesregierung, paragraph 52, and Udlændinge- og Integrationsministeriet, paragraph 31. 35 Judgments in Tjebbes and Others, paragraph 35, and Udlændinge- og Integrationsministeriet, paragraph 32. 36 European Convention on Nationality, adopted on 6 November 1997 by the Council of Europe, entered into force on 1 March 2000. That convention has been applicable to Germany since 1 September 2005. Under Article 7(1)(a) ‘a State Party may not provide in its internal law for the loss of its nationality ex lege or at the initiative of the State Party except [inter alia, in the case of] … voluntary acquisition of another nationality’. 37 As regards that objective, although multiple nationality is supposed to be the exception, academic writers state that dual nationality is more generally accepted today. According to those writers, ‘in practice there has been an enormous increase of naturalisations in acceptance of dual nationality’. See, in that regard, Farahat, A. and Hailbronner, K., op. cit., pp. 9, 18 and 32. Furthermore, it is apparent from the orders for reference that the Convention of 6 May 1963 on the Reduction of Cases of Multiple Nationality and on Military Obligations in Cases of Multiple Nationality, which entered into force, as regards the Federal Republic of Germany, on 18 December 1969, ceased to apply in Germany with effect from 21 December 2002, by virtue of termination. In that regard, those writers explain that the reform of the RuStAG was accompanied by a decision to renounce that convention, which provides only for a very restricted acceptance of dual nationality. 38 The German Government cites the decision of 8 December 2006, 2 BvR 1339/06, DE:BVerfG:2006:rk20061208.2bvr133906, paragraph 14. That government states that it is also apparent from the national case-law that, since the reform of the RuStAG, the suppression of multiple nationality is no longer a priority. See Bundesverwaltungsgericht (Federal Administrative Court), judgment of 10 April 2008, 5 C 28.07, DE:BVerwG:2008:100408U5C28.07.0, paragraph 21. 39 See, to that effect, judgments in Tjebbes and Others, paragraph 34, and Wiener Landesregierung, paragraph 54. Although the Court has used the expression ‘undesirable consequences’ in its case-law, I would confess to some doubt as to whether the consequences of a national of a Member State holding multiple nationalities can be described, in general terms, as ‘undesirable’. 40 The explanatory report on that convention (Council of Europe, European Treaty Series, No 166, p. 11) states that ‘[Article 7(1)(a)] allows States Parties to provide for the loss of nationality when there is a voluntary acquisition of another nationality. The word “voluntary” indicates that there was an acquisition as a result of a person’s own free will and not an automatic one (ex lege)’. 41 It is apparent from that report that, in some States, especially when a large proportion of persons wish to acquire or have acquired their nationality, it may be considered that the retention of another nationality could hinder the full integration of such persons. However other States may consider it preferable to facilitate the acquisition of their nationality by allowing persons to retain their nationality of origin and thus further their integration in the receiving State, for example to enable such persons to retain the nationality of other members of the family or to facilitate their return to their country of origin if they so wish. Explanatory report, p. 3. 42 Judgments in Rottmann, paragraphs 55 and 56; Tjebbes and Others, paragraph 40; Wiener Landesregierung, paragraph 58, and Udlændinge- og Integrationsministeriet, paragraph 38. See also point 41 of this Opinion. 43 Judgments in Tjebbes and Others, paragraph 41, and Udlændinge- og Integrationsministeriet, paragraph 39. 44 Judgment in Udlændinge- og Integrationsministeriet, paragraph 43 and the case-law cited. See also point 38 et seq. of this Opinion. 45 Judgment in Udlændinge- og Integrationsministeriet, paragraph 41 and the case-law cited. See point 38 of this Opinion. 46 According to certain academic writers, the entry into force of Paragraph 25 of the StAG ended abuse of the legislative loophole concerning the application of the domestic clause, but ‘unfortunately, the legal change was not noticed by many Turkish citizens and obviously not even by the Turkish authorities. Therefore, it is estimated that 40,000 Turks, almost unnoticed, lost their German nationality after the entry into force of the [StAG]’ (Farahat, A., and Hailbronner, K., op. cit., p. 26, my italics). On that situation, see also McFadden, S.W., op. cit., p. 80. In my opinion, it is difficult to reconcile such measures with the solidarity which is supposed to form the basis of the relationship between a Member State and its nationals, independently of the fact that, as in the present case, nationality has been acquired by naturalisation in the specific context of a legislative loophole regarding the application of the domestic clause. 47 In particular, it is apparent from the legal background set out by the referring court that Paragraph 38 of the Gesetz über den Aufenthalt, die Erwerbstätigkeit und die Integration von Ausländern im Bundesgebiet (Law on the residence, employment and integration of foreign nationals in federal territory) (BGBl. I, p. 162) of 25 February 2008, provides for a former German national to be granted a permanent resident card or residence permit if, at the time of losing German nationality, he or she fulfils certain conditions. According to certain academic writers, the legislature introduced that paragraph in order to grant such permits ‘to Turkish citizens who have involuntarily lost their German nationality, since they were assuming that they could reacquire their Turkish nationality’ (Farahat, A., and Hailbronner, K., op. cit., p. 26, my italics). 48 See, in that regard, point 71 of this Opinion. 49 See point 38 et seq. of this Opinion. 50 See, to that effect, judgments in Tjebbes and Others, paragraph 42, and Udlændinge- og Integrationsministeriet, paragraph 40. 51 See, to that effect, judgments in Tjebbes and Others, paragraph 42, and Udlændinge- og Integrationsministeriet, paragraph 40. 52 The Court has stated that those consequences cannot be hypothetical or merely a possibility. Judgments in Tjebbes and Others, paragraph 44, and Udlændinge- og Integrationsministeriet, paragraph 54. 53 Judgment in Udlændinge- og Integrationsministeriet, paragraph 55 and the case-law cited. 54 In that the applicant had made her application to retain Danish nationality after the time limit laid down by the national legislation had expired. See footnote 25 to this Opinion. 55 This factor converges with the considerations set out in point 66 et seq. of this Opinion. Against that background, the applicants in the main proceedings were able, as German nationals, to exercise the rights attaching to EU citizenship between their naturalisation in 1999 and the adoption of the decision declaring them to have lost their nationality, which is to say for at least 18 years. That situation – considered first of all as a legal situation and then as a factual situation – must be taken into account in the examination of proportionality and, in particular, in the context of the protection of the right to family and professional life. 56 The referring court explains that Paragraph 13 of the StAG, which, under certain conditions, enables facilitated naturalisation of former German citizens, applies only in cases where the applicants reside abroad. 57 Judgment in Udlændinge- og Integrationsministeriet, paragraphs 57 and 58. See also my Opinion in Udlændinge- og Integrationsministeriet, (C‑689/21, EU:C:2023:53, points 93 and 94).