33. The duty to avoid statelessness, outlined in Principle 5.1, is “a fundamental principle of international law 45 and has been acknowledged as an obligation of customary international law.46 According to the UN Secretary General’s Guidance Note on the UN and Statelessness, the avoidance of statelessness exists “as a corollary to the right to nationality itself and “States must make every effort to avoid statelessness through legislative, administrative and other measures .47 34. Based on this principle, the International Law Commission recognises that: “Neither loss of nationality nor denationalization should lead to statelessness. In the case of denationalization in particular, there is a general obligation not to denationalize a citizen who does not have any other nationality”.48 Case law, in particular that of regional human rights courts, has affirmed that States’ discretion to set the rules for acquisition and loss of nationality is limited by their “obligation to prevent, avoid and reduce statelessness 49 and that “the power to deprive a person of his or her nationality has to be exercised in accordance with international standards, to avoid the risk of statelessness .50 35. To render a person stateless through denationalisation would not accord with the understanding that “States should always be guided by the principle that restrictions on the rights of an individual should not impair the essence of the rights .51 To deprive a person of nationality and thereby render them stateless is to deprive the person of the essence of the right to a nationality. It has also been argued that “in so far as deprivation of nationality results in statelessness, it must be regarded as retrogressive .52 36. Article 4(a) ECN stipulates that each State Party’s rules on nationality must be based on the principle that statelessness shall be avoided. Deprivation of nationality which results in statelessness is likely to be disproportionate and therefore arbitrary. A number of other regional instruments also stipulate the prohibition of arbitrary deprivation of nationality (see also Principle 45 UN Human Rights Council, ‘Human rights and arbitrary deprivation of nationality: Report of the Secretary-General’, A HRC , p. . Explanatory Report to the ECN, para 33. 47 UN Secretary-General UNSG , ‘Guidance Note of the Secretary General: The United Nations and Statelessness’ November , available at: https://www.refworld.org/pdfid/5c580e507.pdf, p. 4. 48 International Law Commission, ‘Fourth report on the expulsion of aliens, by Mr. Maurice Kamto, Special Rapporteur’, A CN. 4 (24 March 2008) para 29. 49 IACtHR, Girls Yean and Bosico v Dominican Republic (2005), Series C No. 130, para 140. See also Third Report on the Situation of Human Rights in Chile, IACHR OEA/Ser/L/V/II.40, Doc 10, 11 February 1977, at. 80-1. 50 ACtHPR, Anudo v Tanzania (2018), Application no. 012/2015, para 78. 51 Global Counterterrorism Forum (GCTF), Glion Recommendations on the Use of Rule of Law-Based Administrative Measures in a Counterterrorism Context (25 September 2019), p.2. The Global Counterterrorism Forum (GCTF) is an informal, a-political, multilateral counterterrorism platform working at strengthening the international architecture for addressing terrorism, bringing together states, international and regional organisations, academics and think tanks. See also https://www.thegctf.org/. The GCTF Criminal Justice and Rule of Law Working Group (GCTF CJ-ROL Working Group) has developed these Recommendations, which offer guidance to policy makers, law enforcement officials, and other relevant stakeholders for the design, implementation, and monitoring of administrative measures in accordance with applicable domestic law and in full respect of applicable international law. 52 R. Y. Jennings and A. Watts, Oppenheim’s International Law, 9 th edn.,(London: Longman 1991), 880 as cited in Guy Goodwin-Gill, ‘Deprivation of Citizenship, Statelessness, and International Law: More Authority if it were needed... ’ May p. . 46 32