situations of de jure or de facto discrimination. 135 The Court has also indicated in its case law that, in the current stage of evolution of international law, the fundamental principle of equality and non-discrimination has entered the realm of ius cogens because the entire legal structure of national and international public order rests on it, and it is a fundamental principle that permeates all laws. 136 99. The right to equality and non-discrimination encompasses two concepts: one related to the prohibition of arbitrary differences in treatment, and one related to the obligation of States to create conditions of real equality for groups that have been historically excluded or who are at greater risk of suffering discrimination. 137 100. With respect to the first concept, the Court has stated that not every difference in treatment will be considered discriminatory: it is only considered discriminatory when it has no objective and reasonable justification, 138 that is, when it does not seek a legitimate purpose and when the means used are disproportionate to the purpose sought. 139 Regarding the second concept, States are obliged to take affirmative action in order to reverse or change any discriminatory situations that exist in their societies that prejudice a specific group of persons. This involves the special obligation of protection that the State must exercise with regard to the actions and practices of third parties who, with its tolerance or acquiescence, create, maintain or encourage discriminatory situations. 140 101. In relation to the foregoing, this Court has established that a person’s ethnic origin is a category protected under Article 1(1) of the Convention. Consequently, no norm, decision or practice of domestic law, applied either by State authorities or by private individuals, may reduce or restrict in any way the rights of an individual based on his ethnic origin. 141 The Court has determined that ethnic groups are communities of individuals who share, inter alia, characteristics of a socio-cultural nature, such as cultural, linguistic and spiritual affinities as well as historical and traditional origins. Indigenous peoples fall within this category, and the Court has recognized that they have specific characteristics that comprise their cultural identity, 142 such as their customary law, their economic and social characteristics and their values, practices and customs. 143 102. The Court has also established that, although poverty and disability are not considered special categories of protection in the literal sense of Article 1(1) of the American Convention, Cf. Juridical condition and rights of undocumented migrants. Advisory Opinion OC-18/03 of September 17, 2003. Series A No. 18, para. 103, and Advisory Opinion OC-27/21, supra, para. 152. 135 136 Cf. Advisory Opinion OC-18/03, para. 101, and Advisory Opinion OC-27/21, supra, para. 152. 137 Cf. Advisory Opinion OC-18/03, supra, para. 92, and Advisory Opinion OC-27/21, supra, para. 158. Cf. Case of I.V. v. Bolivia. Preliminary objections, merits, reparations and costs. Judgment of November 30, 2016. Series C No. 329, para. 240, and Advisory Opinion OC-27/21, supra, para. 159. 138 Cf. Case of Norín Catrimán (Leaders, Members and Activist of the Mapuche Indigenous People) et al. v. Chile. Merits, reparations and costs. Judgment of May 19, 2014. Series C No. 279, para. 200, and Advisory Opinion OC-27/21, supra, para. 159. 139 140 Cf. Advisory Opinion OC-18/03, supra, para. 104, and Advisory Opinion OC-27/21, supra, para. 160. Cf. Case of Norín Catrimán et al. (Leaders, Members and Activist of the Mapuche Indigenous People) v. Chile, supra, paras. 204-206. 141 Cf. Case of the Yakye Axa Indigenous Community v. Paraguay. Merits, reparations and costs. Judgment of June 17, 2005. Series C No. 125, para. 51, and Case of Norín Catrimán et al. (Leaders, Members and Activist of the Mapuche Indigenous People) v. Chile, supra, para. 204. 142 Cf. Case of the Yakye Axa Indigenous Community v. Paraguay, para. 63, and Case of Norín Catrimán et al. (Leaders, Members and Activist of the Mapuche Indigenous People) v. Chile, supra, para. 204. 143 35