21. In general, the Mexican Supreme Court of Justice of the Nation (hereinafter, “SCJN”) has used different criteria with regard to the elements required to analyze the constitutionality of a retrogressive measure. 57 In addition, it can be noted that its two chambers have established different tests to analyze the constitutionality of measures that are allegedly retrogressive. According to the First Chamber of the SCJN, a retrogressive measure is constitutional, when any issue relating to budgetary resources is involved, if: (i) a lack of resources is proved; (ii) it is demonstrated that every necessary effort was made to obtain them, unsuccessfully, and (iii) it is proved that the maximum of available resources were applied, or that the resources available were applied to protect another human right (and not any social purpose), and that the relative importance of fulfilling that right first and foremost was greater.58 Meanwhile, the Second Chamber of the SCJN has indicated that to conclude that a retrogressive measure is justified, it is necessary to analyze whether: (i) the essential purpose of this reversion is to increase the level of protection of a human right, and (ii) it creates a reasonable balance between the fundamental rights in play, without having too great effect on the realization of one of them. 59 22. As can be appreciated, different national constitutional jurisdictions have assessed whether there has been a failure to comply with the gradual realization of the ESCER in the context of the principle of progressivity. It should be noted that, even though the Constitutions in the region do not expressly recognize the prohibition of retrogression, the high national jurisdictions have addressed the issue. Thus, as in the case of the CESCR, a prohibition of retrogression exists implicitly within the content of progressivity.60 c. Decisions concerning the right to health of people living with HIV objective; (iv) it does not affect the essential content of the fundamental right involved, and (v) the benefit achieved is proportionate to the cost. Ibidem, pp. 32 and 33. For example, the SCJN has used a generic analysis with regard to the validity of a measure that is supposedly retrogressive, in function of its social purpose (cf. SCJN, First Chamber, Amparo in review 304/2015, Judgment of May 31, 2017, pp. 25 to 28), as well as a test consisting in proving the existence of a general restriction and a causal relationship between the measure and adverse effects on the applicants for amparo (cf. SCJN. Amparo in review 566/2015. Judgment of February 15, 2017, pp. 32 and 33). 57 Cf. SCJN. First Chamber, Amparo in review 750/2015, The Board and treasurer of the Universidad Michoacana de San Nicolás de Hidalgo. Judgment of April 20, 2016, pp. 84 and 85; Cf. SCJN, First Chamber, Amparo in review 1374/2015, Judgment of May 18, 2016, pp. 84 and 85; Cf. SCJN, First Chamber, Amparo in review 1356/2015, Judgment of July 6, 2016, pp. 30 and 31; Cf. SCJN, First Chamber, Amparo in review 100/2016, Judgment of August 10, 2016; Cf. SCJN. First Chamber, Amparo in review 306/2016, Judgment of March 8, 2017, pp. 67 and 68. 58 Cf. SCJN. Second Chamber, Amparo in review 2425/2015, August 12, 2015, p. 16; Cf. SCJN, Second Chamber, Contestation of ruling 291/2015, January 20, 2016, pp. 61 and 62; Cf. SCJN, Second Chamber, Amparo in review 559/2015, February 17, 2016, pp. 21 and 22; Cf. SCJN, Second Chamber, Amparo in review 11/2016, May 18, 2016, p. 25; Cf. SCJN, Second Chamber, Amparo in review 7153/2016, April 5, 2017, pp. 32 and 33. 59 60 In this regard, in its General Comment No. 3 (1991), the CESCR stated, when analyzing the general obligation of progressivity, that: “[…] any deliberately retrogressive measures […] would require the most careful consideration and would need to be fully justified by reference to the totality of the rights provided for in the Covenant and in the context of the full use of the maximum available resources.” This line of interpretation by the Committee on Economic, Social and Cultural Rights has been reiterated in recent Comments, such as General Comment No. 23 (2016) which indicated that: ”State parties should avoid taking any deliberately retrogressive measure without careful consideration and justification. […] States parties facing considerable difficulties in achieving progressive realization of that right due to a lack of national resources have an obligation to seek international cooperation and assistance.” CESCR, General Comment No. 3, The Nature of States Parties’ Obligations (Art. 2, Para. 1, of the Covenant), January 1, 1990, para. 9, and General Comment No. 23 on the right to just and favourable conditions of work (article 7 of the International Covenant on Economic, Social and Cultural Rights), E/C.12/GC/23, April 26, 2016, para. 52. 10