The challenge to an arbitral award pursuant to article 829 of the Code of Civil Procedure constitutes proceedings subject to limited review which does not permit re-examination of the merits of the arbitrators' decision, being confined solely to the *iudicium rescindens* (rescissory judgment) for the determination of the grounds of nullity exhaustively provided for by the provision.
Re-examination of the merits of the arbitral award through the *iudicium rescissorium* (restorative judgment) under article 830 of the Code of Civil Procedure is subject to the preliminary resolution of the question of violation of law that may be raised by way of appeal on points of law and requires the explicit allegation of the erroneousness of the legal principle applied in relation to the elements established by the arbitrators.
The nullity defect of the award under article 829, paragraph 1, n. 12 of the Code of Civil Procedure for failure to decide (*omessa pronuncia*) arises exclusively when the arbitrator fails to consider claims and substantive defences raised by the parties in accordance with the arbitration agreement, and cannot be invoked in respect of mere generic defensive arguments.
The defect of contradictoriness of the arbitral award assumes relevance as a ground of nullity only when there exists evident contradictoriness between the different components of the operative part or between the reasoning and the operative part, whereas internal contradictoriness between different parts of the reasoning is relevant only when it renders absolutely impossible the reconstruction of the logical-legal reasoning of the decision due to the total absence of reasoning.