CYELP 16 [2020] 301-317 305 lity.7 Statelessness is caused especially through: a conflict of nationality laws, state succession (also the rise and fall of states, the legacy of colonisation), arbitrary deprivation of nationality (denationalisation), discrimination (especially against woman in marriage law and through the paternal model of ius sanguinis), the inheritance of statelessness,8 and even the physical disappearance of state territory due to climate change (eg Tuvalu, Kiribati).9 There are also some administrative barriers to civil registration in the host country such as problems with documents, ie the lack of required documentation (including a birth certificate, marriage certification) or the lack of a residence permit. It is necessary to emphasise that statelessness can appear in both migratory and non-migratory contexts. Two differences must be pointed out here. Firstly, there is a distinction between migrants and refugees who are considered to be stateless persons and those whose citizenship is not established. The latter are usually referred to as persons ‘without citizenship’ or ‘undefi ned citizens’,10 which does not automatically mean that they are stateless but derives on many occasions from the fact that they do not want to reveal their identity or citizenship. In such a case, the position of persons with undetermined citizenship − who do not want to officially disclose their citizenship − becomes similar to that of de facto stateless persons because, although they have a nationality, they do not effectively exercise the rights arising from it. Secondly, a distinction between migrants and refugees should be made clear, because persons coming to Europe from Syria, Iraq or Afghanistan during the migration crisis are often granted refugee status.11 The main difference between refugees and migrants is that migrants are people who made their decision to migrate freely, without pressure from external circumstances beyond 7 The Institute on Statelessness and Inclusion, The Norwegian Refugee Council and The Netherlands Organisation for Scientific Research, ‘What Is Statelessness? Toolkit: Understanding Statelessness in the Syria Refugee’ available at <www.syrianationality.org/index. php?id=14> accessed 22 May 2020. 8 Institute on Statelessness and Inclusion, The World’s Stateless (Wolf Legal Publishers 2014) 23-27. 9 See Jane Steffens, ‘Climate Change Refugees in the Time of Sinking Islands’ (2019) 52 Vanderbilt Journal of Transnational Law 727; Jane McAdam, Climate Change, Forced Migration, and International Law (OUP 2012). 10 Estonian law in particular regulates this form of residence. It treats migrants from former Soviet republics and their children who, after the collapse of the Soviet Union, could not or did not want to apply for citizenship of any country as undefined citizens. For differences in national practices that are assessed in the light of the relevant international and EU standards, see Gerard-René De Groot, Katja Swider and Oliver Vonk, Practices and Approaches in EU Member States to Prevent and End Statelessness (European Parliament 2015). 11 An individual can share protection under CRSSP as well as protection under the 1951 Convention relating to the Status of Refugees (CRSR) (and this convention generally ensures more rights than the CRSSP). See UNHCR, Handbook on Protection of Stateless Persons (UNHCR 2014) 31-32.