The duty of arbitrators to invite adversarial debate on issues raised of their own motion, as provided for in Article 101, paragraph 2, of the Code of Civil Procedure, relates exclusively to questions of fact or mixed questions of fact and law which require evidence other than that adduced by the parties, and does not extend to pure questions of law based upon a different legal assessment of the same evidential material already acquired.
An arbitral award which resolves pure questions of law by raising of its own motion the nullity of a contract, based upon the same documents and factual circumstances pleaded by the parties, is not vitiated by nullity for breach of the adversarial principle under Article 829, paragraph 1, n. 9, of the Code of Civil Procedure, being in any event subject to challenge only for breach of the rules of law relating to the merits of the dispute.
A defect in the reasoning of an arbitral award constitutes grounds for nullity under Article 829, paragraph 1, n. 5, of the Code of Civil Procedure, exclusively when the reasoning is entirely absent or so deficient as not to permit comprehension of the logical process of the reasoning followed by the arbitrators and identification of the ratio of the decision adopted.
A challenge to an arbitral award which amounts to mere criticism of the legal assessment made by the arbitrators, aimed at obtaining a renewed examination on the merits of the question, is inadmissible as it falls outside the scope of review provided for by Article 829 of the Code of Civil Procedure.