it would be difficult to justify deprivation of liberty that leads to statelessness as a proportional measure.166 Second, deprivation of nationality must not be arbitrary167 and should meet the following basic requirements: • As far as the deprivation results in restrictions on human rights, it must meet the legal standards to justify restrictions, namely that the limitation is prescribed by law, is necessary for the achievement of a legitimate purpose and proportionate to the intended aim, and is not discriminatory. Laws that allow for nationality to be deprived in cases where it is deemed “conducive to the public good”,168 set a much lower threshold than the one provided by the principles of necessity and proportionality, as required by international human rights law.169 Where someone joining a banned or “extremist” organization is automatically deprived of citizenship, states end up skipping the careful case-by-case consideration of legal tests required by human rights law for taking this action. • It is essential that individuals have a practical and effective right to challenge deprivation of their nationality before a court of law, given the extreme impact such measures may have on human rights. Particular issues arise when, as has happened in practice, individuals do have the right to appeal in theory but are abroad at the relevant time and cannot give meaningful effect to the right in practice.170 • Deprivation of nationality must not be discriminatory. For example, provisions that apply only to naturalized persons have been criticized for creating a group of “second-class citizens”. The “dual nationality rule” (which allows deprivation of citizenship only for dual nationals) has been criticized for the same reason, although it may be seen as a valid consideration to prevent statelessness, because it can be perceived 166 UN Secretary General, UN Doc. A/HRC/25/28, para. 4, op. cit., note 163; see also UN Secretary General, Report to the Human Rights Council (“Human rights and arbitrary deprivation of citizenship”), UN Doc. A/ HRC/13/34, 14 December 2009, para. 59. 167 This is explicit in, for example, Article 15 UDHR; Article 20 ACHR. 168 This standard is employed for example in the United Kingdom under the Immigration Act 2014. See D. Anderson, “Citizenship Removal Resulting in Statelessness, first report of the independent reviewer on the operation of the power to remove citizenship obtained by naturalisation from persons who have no other citizenship”, UK Independent Reviewer of Terrorism Legislation, April 2016, <https://www.gov.uk/government/publications/ citizenship-removal-resulting-in-statelessness>. 169 Similarly, a bill signed into law in Kazakhstan in July 2017 providing for revocation of citizenship of individuals convicted of terrorist crimes and other offences causing grave harm to the country’s vitally important interests has been criticized for its vagueness and potentially broad interpretation, which could contravene those basic requirements, see for example “Nations in Transit 2018, Kazakhstan, Country Profile”, Freedom House, <https:// freedomhouse.org/report/nations-transit/2018/kazakhstan>; “Kazakhstan Adopts Law On Deprivation Of Citizenship”, Radio Free Europe/Radio Liberty, 11 July 2017, <www.rferl.org/a/kazakhstan-citizenship-law-nazarbaev/28610008.html>; C. Putz, “Kazakhstan Considers Revoking Terrorists’ Citizenship”, The Diplomat, 24 May 2017, <https://thediplomat.com/2017/05/kazakhstan-considers-revoking-terrorists-citizenship/>. 170 See, for example, “Foreign Fighters under International Law”, Geneva Academy of International Humanitarian Law and Human Rights, Academy Briefing No. 7, pp. 57-58, <www.geneva-academy.ch/joomlatools-files/docman-files/Publications/Academy%20Briefings/Foreign%20Fighters_2015_WEB.pdf>. Guidelines for Addressing the Threats and Challenges of “Foreign Terrorist Fighters” 49