Clara Van Thillo of the jus soli-principle, nationality is acquired by birth on a State’s territory.48 In States following the jus sanguinis-principle, nationality is acquired at birth on the basis of parental descent.49 While the jus soli-principle is more prevalent in States with a common law heritage and the jus sanguinis-principle in States with a civil law tradition, many States also combine both principles.50 Jus soli-systems are inherently more inclusive, as every individual born on the territory is granted nationality. When a child is born to stateless parents or to parents of unknown nationality in a State solely operating on the basis of the jus sanguinis-principle, the child will be left stateless and the condition becomes hereditary.51 Also in the case of foundlings, the jus sanguinis-principle offers no protection.52 Finally, conflicts of laws emerge due to the co-existence of both systems. For example, when a national moves from a jus solisystem to a jus sanguinis-system, his child born on the territory of the latter will be stateless.53 Regarding relative statelessness, multiple causes were identified, including conflicts of laws. For example, marriage can result in statelessness when nationality laws provide for the loss of a woman’s nationality when she marries a man of another nationality, even though she does not acquire her husband’s nationality.54 State succession can also cause statelessness, as this necessarily involves a change of nationality. When inhabitants of the territories concerned do not retain their former nationality and are excluded from the treaty determining the beneficiaries of the nationality of the new State, they are rendered stateless.55 Unilateral acts of nationality deprivation by the State can also result in relative statelessness. A distinction was made between denationalisation, i.e. when the provisions apply to all nationals, and denaturalisation, i.e. when the provisions only apply to naturalised nationals.56 Denationalisation can take effect by operation of the law (collective denationalisation), or by a judicial or administrative decision (individual denationalisation).57 Finally, an individual can also become stateless by means of his own unilateral act. Nationality laws may provide for a right of expatriation, meaning that nationals can voluntarily renounce their nationality.58 If the individual cannot obtain any another nationality when receiving an expatriation permit, he becomes stateless.59 48 Paul Weis, Nationality and Statelessness in International Law (2nd ed., Sijthoff & Noordhoff 1979), 95. 49 ibid. 50 Ivan Shearer and Brian Opeskin, ‘Nationality and Statelessness’ in Brian Opeskin, Richard Perruchoud and Jillyanne Redpath-Cross (eds), Foundations of International Migration Law (1st ed., Cambridge University Press 2012), 98-99. 51 International Union for Child Welfare, Stateless Children: A Comparative Study of National Legislations and Suggested Solutions to the Problem of Statelessness of Children (International Union for Child Welfare 1947), 15-16. 52 ibid, 14. 53 ibid, 22. 54 Weis, ‘Statelessness as a legal political problem’ (n 13), 5. For an extensive analysis of statelessness resulting from marriage, see Catheryn Seckler-Hudson, Statelessness: With Special Reference to the United States: A Study in Nationality and Conflict of Laws (Digest Press 1934). 55 Rudolf Graupner, ‘Statelessness as a Consequence of the Change of Sovereignty over Territory after the Last War’ in Paul Weis and Rudolf Graupner (eds), The Problem of Statelessness (World Jewish Congress 1944), 30; Weis, ‘Statelessness as a legal political problem’ (n 13), 5. 56 Weis, ‘Statelessness as a legal political problem’ (n 13), 6. 57 ibid; ILC ‘Report on Nationality, Including Statelessness by Mr. Manly O. Hudson, Special Rapporteur’ (1952) Yearbook of the International Law Commission 1952, Vol. 2, 18. 58 Weis, ‘Statelessness as a legal political problem’ (n 13), 6. 59 ILC ‘Report on Nationality, Including Statelessness by Mr. Manly O. Hudson, Special Rapporteur’ (1952) Yearbook of the International Law Commission 1952, Vol. 2, 18. 6 Academy of European Law