21 57. In line with prior decisions and international law,41 this Court takes the view that, once a State has adopted a position producing certain legal effects, may not, under the principle of estoppel and the rule of non concedit venire contra factum proprium, later assume a position in contradiction to the former one and changing the state of affairs upon which the other party relied.42 Besides, this Tribunal43 has applied the principle of estoppel to grant full effects to the acknowledgment of responsibility made by the State, which purported to disavow in subsequent stages of the proceeding.44 58. Particularly, as to the effect that such positions of acknowledgment may produce during the processing of the case before the Commission, the Tribunal determined in another case against Perú that: Each act of acknowledgment made by Perú before the Commission created estoppel. Therefore, by admitting the legitimacy of the claim asserted in the proceeding before the Commission through a unilateral juristic act of acknowledgement, Perú [was] barred from adopting a contradictory position thereafter. The alleged victims [and] their representatives, as well as the Inter-American Commission, acted in the proceeding before the latter body on the basis of the position of acknowledgment taken up by the State.45 59. Furthermore, the positions of acknowledgment made during the processing of an application before the Commission are necessarily relevant to determine the application of the principle of estoppel regarding contradictory positions alleged during the processing of the case before the Court. All this because, in accordance with Article 61.2 of the American Convention, a proceeding cannot be brought before the Inter-American Court without having initiated a previous procedure before the Inter-American Commission and having exhausted the remedies stipulated in Articles 48 to 50 of said treaty. Consequently, the controversy that the Commission submitted to the Court's jurisdiction must stick to the report considered in Article 50 of the Convention. Therefore, if the controversy brought before the Tribunal is necessarily based on the said report, and rests on certain positions of acknowledgment made by the State during the procedure before the Commission, then the State cannot denied the legal effect that said statements have on the determination of the controversy that the Commission submits to the Court. 60. However, not every position adopted within the framework of the 41 Cf. Territorial Dispute (Libyan Arab Jamahiriya/Chad), I.C.J. Reports 1994, Judgment of February 3, 1994, paras. 56, 68, 75; Nuclear Tests (Australia v. France), I.C.J. Reports 1974, Judgment of December 20, 1974, paras. 42-46, and Temple of Preah Vihear (Cambodia v. Thailand), I.C.J. Reports 1962, Judgment of June 15, 1962, para. 32. 42 Cf. Case of Neira Alegría et al. V. Perú. Preliminary Objections. Judgment of December 11, 1991. Series C No. 13, para. 29; Case of the Rochela Massacre V. Colombia. Merits, Reparations and Costs. Judgment of May 11, 2007. Series C No. 163, para. 46; and Case of the Dismissed Congressional Employees (Aguado - Alfaro et al.) v. Perú. Preliminary Objections, Merits, Reparations and Costs. Judgment of November 24, 2006. Series C Nº 158, para. 60. 43 The European Court of Human Rights has also applied the principle of estoppel regarding objections over the jurisdiction and admissibility put forward by the State in an untimely way. Cf. ECHR, Case of Mizzi v. Malta, Judgment of 12 January 2006, no. 26111/02, para 43-48; Case of Tuquabo-tekle and others v. The Netherlands, Judgment of 1 December 2005, no. 60665/00, para. 26-32; Case of Artico v. Italy, Judgment of 13 May 1980, Serie A no. 37, para. 25-28,and Case of De Wilde, Ooms and Versyp v. Belgium, Judgment of 18 June 1971, Serie A no. 12, para. 58-59. 44 Cf. Case of The Caracazo V. Venezuela. Reparations and Costs. Judgment of August 29, 2002. Series C No. 95, para. 52; Case of the Rochela Massacre, supra nota 42, para. 46 and 48; Case of Montero Aranguren et al. (Retén de Catia) V. Venezuela. Preliminary Objection, Merits, Reparations and Costs. Judgment of July 5, 2006. Series C No. 150, para. 49. 45 Cf. Case of Acevedo Jaramillo et al. V. Perú. Preliminary Objections, Merits, Reparations and Costs. Judgment of February 7, 2006. Series C No. 144, para. 177.