Nationality in relation to the succession of States Other criteria such as the place of birth or the legal bond with a constituent unit of the predecessor State, however, become significant for the determination of the nationality of persons concerned who have their habitual residence outside the territory of a successor State, in particular when they lose the nationality of the predecessor State as a consequence of the latter’s disappearance. SECTION 1. TRANSFER OF PART OF THE TERRITORY Article 20. Attribution of the nationality of the successor State and withdrawal of the nationality of the predecessor State When part of the territory of a State is transferred by that State to another State, the successor State shall attribute its nationality to the persons concerned who have their habitual residence in the transferred territory and the predecessor State shall withdraw its nationality from such persons, unless otherwise indicated by the exercise of the right of option which such persons shall be granted. The predecessor State shall not, however, withdraw its nationality before such persons acquire the nationality of the successor State. Commentary (1) Section 1 consists of a single article, namely article 20. As indicated by the opening phrase “When part of the territory of a State is transferred by that State to another State”, article 20 applies in the case of cessions of territory between two States on a consensual basis. While this phrase refers to standard modes of transfer of territory, the substantive rule embodied in article 20 also applies mutatis mutandis to the situation where a dependent territory becomes part of the territory of a State other than the State which was responsible for its international relations, that is, the case of a Non-Self-Governing Territory which achieves its decolonization by integration with a State other than the colonial State. (2) The rule in article 20 is based on the prevailing State practice:114 persons concerned who have their habitual residence in the transferred territory acquire the nationality of the successor State and consequently lose the nationality of the predecessor State, unless they opt for the retention of the latter’s nationality.115 (3) As to the effective date on which persons concerned who have not exercised the right of option become nation- 41 als of the successor State, the Commission believes that it depended on the specific character of the transfer: thus, when a transfer of territory involves a large population, such change of nationality should take effect on the date of the succession; on the contrary, in cases of transfers involving a relatively small population, it may be more practical that the change in nationality take place on the expiration of the period for the exercise of the option. The latter scenario is not inconsistent with the presumption in article 5 of automatic change of nationality on the date of the succession, since the said presumption is rebuttable as explained in the commentary to that article. (4) Whatever the date of the acquisition of the nationality of the successor State, the predecessor State must comply with its obligation to prevent statelessness under article 4, and shall therefore not withdraw its nationality before such date.116 (5) Although there have been a number of instances where the right to opt for the retention of the nationality of the predecessor State was granted only to some categories of persons residing in the transferred territory, the Commission considers that all such persons should be granted this right, even if this were to entail a progressive development of international law. The Commission does not believe that it is necessary to address in article 20 the question whether there are any categories of nationals of the predecessor State having their habitual residence outside the transferred territory who should be granted a right to opt for the acquisition of the nationality of the successor State. Naturally, the successor State remains free, subject to the provisions of article 8, to offer its nationality to such persons when they have an appropriate connection with the transferred territory. (6) In the Commission’s view, persons concerned who have opted for the nationality of the predecessor State under the terms of article 20, thereby cancelling the presumption in article 5, should be deemed to have retained such nationality from the date of the succession. Thus, there would be no break in the continuity of the possession of the nationality of the predecessor State. SECTION 2. UNIFICATION OF STATES Article 21. Attribution of the nationality of the successor State Subject to the provisions of article 8, 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 114 See paragraphs (1) to (27) of the commentary to draft article 17 proposed by the Special Rapporteur in his third report (footnote 10 above). 115 See also article 18, paragraph (b) of the Draft Convention on Nationality prepared by Harvard Law School which provided that “[w]hen a part of the territory of a State is acquired by another State . . . , the nationals of the first State who continue their habitual residence in such territory lose the nationality of that State and become nationals of the successor State, in the absence of treaty provisions to the contrary, unless in accordance with the law of the successor State they decline the nationality thereof” (Research in International Law . . . (footnote 19 above), p. 15). 116 In the same spirit, provision 12 of the Venice Declaration (see footnote 16 above) provides that “[t]he predecessor State shall not withdraw its nationality from its own nationals who have been unable to acquire the nationality of a successor State”. The Convention on the Reduction of Statelessness addresses the problem of statelessness in case of a transfer of territory from a different perspective: article 10, paragraph 2, provides that, should a person concerned become stateless as a result of the transfer, and in the absence of relevant treaty provisions, the successor State shall attribute its nationality to such person.