The challenge to an arbitral award is structured as a form of rescissory challenge, articulated in a first phase aimed at ascertaining the nullities provided for by art. 829 of the Code of Civil Procedure and in a possible second rescissory phase in which the judge proceeds to reconstruct the facts, with the consequence that the re-examination of the merits constitutes an eventual and not principal object of the appeal.
The institutional nature of arbitration is not modified by the authorisation granted to the arbitrators to decide ex bono et aequo or without procedural formalities, the choice of the methods by which the arbitrators must provide for the instruction or decision of the case remaining with the parties.
The ground of nullity referred to in art. 829 para. 1 no. 4 of the Code of Civil Procedure, in the formulation subsequent to Legislative Decree 40/2006, constitutes a closing provision suitable to govern all cases in which the arbitrators have erroneously ruled on the merits notwithstanding the absence of a procedural prerequisite, including also the case of an award that incurs the defect of ultra petita for having admitted and ruled on a new claim or one never raised.