52 Parties have the specific and constant obligation to advance as rapidly and efficiently as possible towards the full realization of this right,208 subject to available resources, by legislation or other appropriate means.209 There is also an obligation of non-retrogression regarding the realization of the rights attained.210 Consequently, the obligations to respect and guarantee rights established in the Convention, as well as domestic legal effects (Articles 1(1) and 2 of the American Convention), are essential to achieve their effectiveness. 191. However, the Court notes that the instant case does not concern the obligations of progressive development derived from Article 26 of the American Convention, but rather the failure to implement the right to a pension as an integral part of Mr. Muelle Flores’ right to social security, owing to the failure to execute and comply with the judgments handed down in his favor in the domestic courts, in the context of the privatization of the State company, following his retirement. Mr. Muelle Flores acquired his right to a pension under a State-administered contributory system; that is, he acquired the right to receive a pension after having paid his contributions for several years. The legality of his enrolment in this system was confirmed at the domestic level (supra para. 74). 192. Accordingly, based on the criteria and constituent elements of the right to social security, and taking into account the facts and specificities of this case, the State’s obligations in relation to the right to a pension are as follows: a) the right to access a pension after reaching the legal age for that purpose and the requirements established by national law, for which there must be a functioning social security system that guarantees benefits. This system should be administered or supervised and audited by the State (in the case of a privately administered system); b) guarantee that the benefits are adequate in amount and duration, to provide the pensioner with a decent standard of living and adequate access to health care, without discrimination; c) ensure the accessibility of the pension, that is, reasonable, proportionate and transparent conditions of access. Also, the cost of the contributions must be affordable and the beneficiaries must receive clear and transparent information, especially if any measure is adopted that could affect their right, such as the Economic, Social and Cultural Rights, General Comment No. 19, The right to social security (Article 9), February 4, 2008, para. 40. 208 Cf. UN, Committee on Economic, Social and Cultural Rights, General Comment No. 3: The Nature of States Parties’ Obligations (Art. 2, Para. 1, of the Covenant), December 14, 1990, U.N. Doc. E/1991/23, para. 9, and Committee on Economic, Social and Cultural Rights, General Comment No. 19, The right to social security (Article 9), February 4, 2008, paras. 40 and 41. 209 Article 26 of the Convention establishes: “Article 26. Progressive Development. The States Parties undertake to adopt measures, both internally and through international cooperation, especially those of an economic and technical nature, with a view to achieving progressively, by legislation or other appropriate means, the full realization of the rights implicit in the economic, social, educational, scientific, and cultural standards set forth in the Charter of the Organization of American States as amended by the Protocol of Buenos Aires, subject to available resources, by legislation or other appropriate means.” 210 Cf. Case of Acevedo Buendía et al. (“Discharged and Retired Employees of the Comptroller’s Office”) v. Peru, supra, paras. 102, 103, and Case of Poblete Vilches et al. v. Chile. Merits, reparations and costs. Judgment of March 8, 2018. Series C No. 349, para. 104. See also: “Working Group to Examine the National Reports envisioned in the Protocol of San Salvador”. Initially, the Working Group prepared the document “Progress indicators for measuring rights under the Protocol of San Salvador,” OEA/Ser.L/XXV.2.1; GT/PSS/doc.2/11 rev.2, of December 16, 2011, based on the guidelines and criteria presented by the Inter-American Commission on Human Rights. Following consultations with the States and civil society, these were adopted by the Forty-second General Assembly held in Cochabamba, Bolivia in June 2012 (AG/RES. 2713 (XLII-O/12). On that occasion, the rights to social security, health and education were addressed. Subsequently, a second group of rights was addressed and the Working Group issued the “Progress indicators for measuring rights contemplated in the Protocol of San Salvador – second group of rights,” OEA/Ser.L/XXV.2.1 GT/PSS/doc.9/13, adopted by the OAS General Assembly in Resolution AG/RES. 2823 (XLIV-O/14), at the second plenary session on June 4, 2014. Finally, in 2015, the Working Group combined the two groups of rights and published the document “Progress indicators for measuring rights contemplated in the Protocol of San Salvador,” OEA/Ser.D/XXVI.11 (2015). On that occasion, they addressed the right to work and trade union rights, the right to adequate food, a healthy environment, and the benefits of culture. Cf. UN, Committee on Economic, Social and Cultural Rights, General Comment No. 19. The right to social security (Art. 9 of the Covenant), February 4, 2008, para. 42.