42 Report of the International Law Commission on the work of its fifty-first session one of the States which have united, the successor State shall attribute its nationality to all persons who, on the date of the succession of States, had the nationality of a predecessor State. Commentary (1) Section 2 also consists of one article, namely article 21. As indicated by the phrase “when two or more States unite and so form one successor State, irrespective of whether the successor State is a new State or whether its personality is identical to that of one of the States which have united”, article 21 covers the same situations as those described in the commentaries to the draft articles on succession of States in respect of treaties117 and those on succession of States in respect of State property, archives and debts118 concerning the case of unification of States. The Commission finds it preferable to spell out the two possible scenarios in the text of the article itself. (2) The unification of States envisaged in article 21 may lead to a unitary State, to a federation or to any other form of constitutional arrangement. It must be emphasized, however, that the degree of separate identity retained by the original States after unification in accordance with the constitution of the successor State is irrelevant for the operation of the provision set forth in this article.119 It must also be stressed that article 21 does not apply to the establishment of an association of States which does not have the attributes of a successor State.120 (3) As the loss of the nationality of the predecessor State or States is an obvious consequence of territorial changes resulting in the disappearance of the international legal personality of such State or States, the main problem addressed in this article is that of the attribution of the nationality of the successor State to persons concerned. In this case, the term “persons concerned” refers to the entire body of nationals of the predecessor State or States, irrespective of the place of their habitual residence. (4) Accordingly, article 21 provides that, in principle, the successor State has the obligation to attribute its nationality to all persons concerned. As regards, however, a person concerned who has his or her habitual residence outside the territory of the successor State and also has another nationality, whether that of the State of residence or that of any other third State, the successor State may not attribute its nationality to such person against his or 117 Yearbook . . . 1974, vol. II (Part One), pp. 253-260, document A/ 9610/Rev.1, commentary to draft articles 30 to 32. 118 Yearbook . . . 1981, vol. II (Part Two), p. 43, document A/36/10, commentary to draft article 15. 119 This was also the view expressed by the Commission in relation to draft articles 30 to 32 on the succession of States in respect of treaties. See paragraph (2) of the commentary to those articles (footnote 117 above). 120 This is for instance the case of the European Union, despite the fact that the Treaty on European Union (Maastricht Treaty) established a “citizenship of the Union”. Under the terms of article 8, “[e]very person holding the nationality of a member State shall be a citizen of the Union”. The Commission notes that the concept of citizenship of the European Union does not correspond to the concept of nationality as envisaged in the present draft articles. her will. This exception is taken into account by the inclusion of the phrase “Subject to the provisions of article 8”. (5) The provision in article 21 reflects State practice. Where unification has involved the creation of a new State, such State attributed its nationality to the former nationals of all States that merged, as did, for instance, the United Arab Republic in 1958121 and Tanzania in 1964.122 Where unification has occurred by incorporation of one State into another State which has maintained its international personality, the latter extended its nationality to all nationals of the former.123 This was the case, for example, when Singapore joined the Federation of Malaysia in 1963.124 The Commission believes that the rule set forth in article 21 is sufficiently broad as to cover the obligations of a successor State under both scenarios. (6) The Commission is of the view that article 21 embodies a rule of customary international law. In any event, the successor State, which after the date of the succession, is the only remaining State concerned cannot conclude an agreement with another State concerned which would depart from the above provision. It would be, moreover, difficult to imagine how the successor State could “give effect to the provisions of Part I” in a different manner. 121 Article 2 of the Provisional Constitution of the United Arab Republic of 5 March 1958 provided that “[n]ationality of the United Arab Republic is enjoyed by all bearers of the Syrian or Egyptian nationalities; or who are entitled to it by laws or statutes in force in Syria or Egypt at the time this Constitution takes effect” (text reproduced in E. Cotran, “Some legal aspects of the formation of the United Arab Republic and the United Arab States”, The International and Comparative Law Quarterly, vol. 8 (1959), p. 374). This provision was reenacted in article 1 of the Nationality Law of the United Arab Republic No. 82 of 1958 (ibid., p. 381). 122 According to Part II, section 4, subsections (1), (2) and (3) of the Tanzania Citizenship Act, 1995, aimed at consolidating the law relating to citizenship, “[e]very person who . . . was immediately before Union Day a citizen . . . of the Republic of Tanganyika or of the People’s Republic of Zanzibar shall be deemed to have become, on Union Day, . . . a citizen . . . of the United Republic”. These provisions encompass persons who became citizens of any of the two predecessor States by birth, registration, naturalization or by descent. 123 The Draft Convention on Nationality prepared by Harvard Law School only dealt with the case of unification by incorporation. Paragraph (a) of article 18 provided that, “[w]hen the entire territory of a state is acquired by another state, those persons who were nationals of the first state become nationals of the successor state, unless in accordance with the provisions of its law they decline the nationality of the successor state” (Research in International Law . . . (footnote 19 above), p. 15). The comment to this provision stressed that this rule “is applicable to naturalized persons as well as to those who acquired nationality at birth” (ibid., p. 61). 124 Upon unification, persons who had been citizens of Singapore acquired the citizenship of the Federation, but also maintained the status of citizens of Singapore as one of the units constituting the Federation (Goh Phai Cheng, Citizenship Laws of Singapore (Singapore, Educational Publications, 1970), pp. 7-9). For other cases of unification by incorporation, namely the incorporation of Hawaii into the United States of America and the reunification of Germany, see paragraphs (2), (5) and (6), respectively, of the commentary to draft article 18 proposed by the Special Rapporteur in his third report (footnote 10 above).