The challenge to an arbitral award for nullity pursuant to Article 829 of the Code of Civil Procedure has the character of a limited challenge, being admitted exclusively for procedural defects and for non-observance of rules of law within the limits strictly provided by the statute, and is structured in a rescissory phase aimed at ascertaining the existence of nullities and in a possible restitutory phase of review on the merits.
The contradictory nature of an arbitral award, as a cause of nullity under Article 829, paragraph 1, No. 11 of the Code of Civil Procedure, occurs when there emerges a conflict between the different components of the operative part or between the reasoning and the operative part, whereas internal contradiction between different parts of the reasoning constitutes a defect only when it prevents the reconstruction of the logical-juridical process due to a total absence of reasoning attributable to the functional model.
In the rescissory phase of proceedings challenging an arbitral award for nullity, it is not permitted to proceed with findings of fact nor to contest the evaluation of facts adduced by the parties and of evidence acquired in the arbitral proceedings, the judge being required to limit himself to ascertaining any causes of nullity provided for by Article 829 of the Code of Civil Procedure.
In arbitration, where the parties have not bound the arbitrators to observe the rules of the Code of Civil Procedure, the parties are permitted to modify and expand their initial claims without application of procedural preclusions, subject to respect for the principle of due process.
The obligation of arbitrators to observe the rules of the Code of Civil Procedure must derive from an express and unequivocal manifestation of the parties' will, and cannot be inferred tacitly from procedural objections raised during the course of the arbitral proceedings.
The objection of lack of jurisdiction of the arbitrators for a decision beyond the limits of the arbitration agreement must be raised during the course of the arbitral proceedings on pain of inadmissibility of the challenge, pursuant to Article 817 of the Code of Civil Procedure.
The nullity of court-appointed technical consultancy in arbitral proceedings for violation of due process in the acquisition of information from third parties not involved in the proceedings requires proof of a causal link between the irregularity complained of and the content of the expert report, mere allegation of the vitiating event not being sufficient.