92. A legal standard on deprivation of nationality may not be enacted with retroactivity ‘nulla perditio, sine praevia lege’). States are, however, allowed to retroactively enact laws that restrict deprivation of nationality. 93. States sometimes try to deprive persons of their nationality by applying new laws retroactively. The principle of legal certainty, however, prevents States from using their power to deprive a person of his nationality retroactively.168 94. The power to deprive a person of his nationality should be with an appropriate and legally vested competent authority, whose powers on this matter are clearly established by law. The authority should be appropriate in the sense that it is suited and possesses sufficient expertise to deal with matters of nationality deprivation and should be at the appropriate level of responsibility. Officials authorised to deprive a person of nationality must be authorised by law. Their functions (and procedures for deprivation of nationality see also Principle 7.6 on procedural safeguards) must also be clearly established by law. 95. Some further guidance on this is provided by the Tunis Conclusions on Article 8(4) of the 1961 Convention: “Given the serious criminal nature of many of the acts which give rise to deprivation of nationality, participants underlined that where criminal conduct is alleged, it is strongly advisable that deprivation of nationality only occur following a two-step process, logically beginning with a finding of guilt by a criminal court. A decision by the competent authority (preferably a court) on deprivation of nationality would follow.”169 96. The importance of a “competent authority with regard to loss of nationality due to undesirable behaviour has been often highlighted. In light of the principle or proportionality, loss of nationality in such circumstances should always occur “by deprivation of through means of an explicit decision by competent authorities .170 97. Case law of the Inter-American Court of Human Rights on the prohibition of arbitrary deprivation of nationality in the ACHR171 provides an example of when authorities’ lack of competence- and in particular the lack of appropriate level of decision-making - leads to arbitrariness in nationality deprivation. In this case of Ivcher-Bronstein v. Peru, “[…] the authorities who annulled Mr. Ivcher’s nationality title did not have competence. […] Mr. Ivcher Bronstein acquired Peruvian nationality through a “supreme resolution” of the President, and his nationality title was signed by the Minister for Foreign Affairs; however, he lost his nationality as the result of a “‘directorial resolution’ of the Migration and Naturalization Directorate”, which is undoubtedly of a lower rank than the authority that granted the corresponding right […], and, consequently, could not deprive the act of a superior of its effects. Once again, this demonstrates the arbitrary character of the 168 Dutch Council of State 17 April 2019, ECLI:NL:RVS:2019:990; Dutch Council of State 17 April 2019, ECLI:NL:RVS:2019:1246. UNHCR, ’Tunis Conclusions‘ , para . 170 ILEC Guidelines (2015), section IV.3.b See also CJEU, M.G. Tjebbes and Others v Minister van Buitenlandse Zaken (2019), Case C-221/17. 171 Art. 20(3) ACHR. 169 54