The preclusion provided for in Article 817, paragraph 2, of the Code of Civil Procedure, which prevents a party from challenging the award on grounds of non-existence, invalidity or ineffectiveness of the arbitration agreement where that party has not raised the lack of jurisdiction of the arbitrators in the first defence following acceptance, operates exclusively against a party that has participated in the arbitral proceedings, and not against a party that has remained in default, since substantial acquiescence capable of establishing arbitral jurisdiction cannot be inferred from non-participation in the arbitral proceedings.
The finding, with res judicata effect, of the apocryphal nature of the signature affixed to the contract containing the arbitration clause entails the non-existence of the arbitration agreement and results in the nullity of the award pursuant to Article 829, paragraph 1, No. 1, of the Code of Civil Procedure.
The setting aside of an arbitral award for invalidity of the arbitration agreement pursuant to Article 829, paragraph 1, No. 1, of the Code of Civil Procedure results solely in a declaration of nullity of the award, without the court hearing the challenge being entitled to proceed to a decision on the merits of the dispute, since the transition from the rescinding phase to the substitutive phase provided for in Article 830, paragraph 2, of the Code of Civil Procedure is limited exclusively to the grounds of nullity exhaustively listed therein.