particularly, to exercise its functions in the procedure to process individual petitions established in Articles 44 to 51 of the Convention. However, in matters that it is examining, the Court has the authority to carry out a control of the legality of the Commission’s actions. 17 This does not necessarily mean reviewing the proceedings that have been conducted before the Commission, unless one of the parties proves that a serious error has occurred that allegedly violates their right of defense. 18 In addition, the Court must ensure a just balance between the protection of human rights, the ultimate purpose of the inter-American human rights system, and the legal certainty and procedural balance that safeguards the stability and reliability of the international protection. 19 26. The Court has indicated that the processing of individual petitions is governed by guarantees to ensure that the parties can exercise their right of defense during the proceedings. These guarantees are: (a) those related to the admissibility conditions of the petitions (Articles 44 to 46 of the Convention 20), and (b) those related to the adversarial principle (Article 48 of the Convention) and procedural balance. 21 The principle of legal certainty must also be taken into consideration. 22 27. Furthermore, it has been the Court’s consistent case law that the party affirming that an act of the Commission during the proceedings before it has involved a serious error that harms that party’s right of defense must prove this harm. Consequently, in this regard, a mere complaint or difference of opinion is not sufficient in relation to the actions of the InterAmerican Commission. 23 28. In this case, the petition was received on February 12, 1998 (supra para. 2.a) and was forwarded to the State on December 21, 2001; hence, it spent three years and ten months at the initial review stage. 24 Consequently, taking into account the State’s arguments, the Court will now proceed to review the Commission previous actions and decisions in order to monitor that the admissibility requirements, and also the adversarial principle, procedural balance, and legal certainty were observed (supra para. 26). 17 Cf. Control of Legality in the Exercise of the Authority of the Inter-American Commission on Human Rights (Arts. 41 and 44 to 51 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 Furlan and family members v. Argentina. Preliminary objections, merits, reparations and costs. Judgment of August 31, 2012. Series C No. 246, para. 48. 18 Cf. Case of the Dismissed Congressional Employees (Aguado Alfaro et al.) v. Peru. Preliminary objections, merits, reparations and costs. Judgment of November 24, 2006. Series C No. 158, para. 66, and Case of Furlan and family members v. Argentina, supra, para. 48. 19 Cf. Case of Cayara v. Peru. Preliminary objections. Judgment of February 3, 1993. Series C No. 14, para. 63, and Case of Furlan and family members v. Argentina, supra, para. 48. 20 Cf. Case of Velásquez Rodríguez v. Honduras. Preliminary objections. Judgment of June 21, 1987. Series C No. 1, para. 85, and Case of Furlan and family members v. Argentina, supra, para. 49. 21 Cf. Control of Legality in the Exercise of the Authority of the Inter-American Commission on Human Rights (Arts. 41 and 44 to 51 of the American Convention on Human Rights), supra, para. 27, and Case of Furlan and family members v. Argentina, supra, para. 49. 22 Cf. Control of Legality in the Exercise of the Authority of the Inter-American Commission on Human Rights (Arts. 41 and 44 to 51 of the American Convention on Human Rights), supra, para. 27, and Case of Furlan and family members v. Argentina, supra, para. 49. 23 Cf. Case of the Dismissed Congressional Employees (Aguado Alfaro et al.) v. Peru, supra, para. 66, and Case of Furlan and family members v. Argentina, supra, para. 50. 24 Cf. Charter of the Inter-American Commission forwarded to the Minister for Foreign Affairs, International Trade and Worship on December 21, 2001 (file of proceedings before the Commission, folio 524). 12