- 12 - legality of the Commission’s actions in relation to the matters that it is examining.27 Thus, it has been the Court’s consistent case law that the party affirming that an action by the Commission during the procedure before it has been irregular, affecting its right of defense, must provide effective proof of the said prejudice. In this regard, a mere complaint or difference of opinion regarding the Inter-American Commission’s actions is not sufficient.28 24. In the instant case, the Court finds that, what the State considered a serious error that prejudiced it, is, in fact, a difference of opinion concerning the value that, according to the State, the Commission should have accorded to its actions before and after the issue of the Merits Report. The Court notes that the Commission referred to and ruled on the information provided by the State, both in the Merits Report and in the brief submitting the case to the Court; therefore, the Court considers that the Commission did not commit an error in the processing of the case before it for the reasons alleged by the State. 25. Additionally, the Court notes that the State has not demonstrated the specific prejudice resulting from the Commission’s failure to rule on the principle of complementarity, because assessment of the measures implemented by the State is a matter that can still be argued and proved before the Court. That said, the State’s allegations regarding the measures taken following the Merits Report are matters that it is for this Court to decide when analyzing the merits of the case and any possible reparations. 26. Consequently, the Court concludes that the State's allegations regarding the supposed violation of the principles of legal certainty and procedural balance and its right of defense constitute a difference of opinion with regard to what the Commission substantiated and decided, and this should be analyzed when examining the merits of the case and not as a preliminary objection. 27. Based on the foregoing, the Court rejects the preliminary objection filed by the State. V THE STATE’S ACKNOWLEDGEMENT OF RESPONSIBILITY A. The State’s acknowledgement of Commission and the representatives responsibility and observations of the 28. The State made an acknowledgment of responsibility indicating that it did not question or doubt “the human rights violations committed against the victims, and that it had not done so during the merits stage of the procedure before the Inter-American Commission on Human Rights.”29 However, regarding the context in which the facts took place, the State limited its Cf. Control of Due Process in the Exercise of the Powers of the Inter-American Commission on Human Rights (Arts. 41 and 44 of the American Convention on Human Rights). Advisory Opinion OC-19/05 of November 28, 2005. Series A No. 19, first and third operative paragraphs, and Case of Amrhein et al. v. Costa Rica. Preliminary objections, merits, reparations and costs. Judgment of April 25, 2018. Series C No. 354, para. 68. 27 Cf. Case of the Saramaka People v. Suriname. Preliminary objections, merits, reparations and costs. Judgment of November 28, 2007. Series C No. 172, para. 32, and Case of the Dismissed PetroPeru Workers et al. v. Peru. Preliminary objections, merits, reparations and costs. Judgment of November 23, 2017. Series C No. 344, para. 51. 28 The State acknowledged its international responsibility for the violations committed in this case for the first time and in more general terms before the Inter-American Commission on March 14, 2013, during a public hearing held before the Commission during its 147th regular session. Cf. Video of the State's intervention during the public hearing held before the Inter-American Commission on March 14, 2013 (evidence file, file of audiovisual material); communication of the State of 29