The challenge of an arbitral award for violation of rules of law pursuant to Article 829 of the Code of Civil Procedure is not permitted in respect of matters concerning the arbitrators' evaluation of evidential findings which directly relate to the merits of the dispute. Any claim of nullity must be anchored to the factual elements established by the arbitrators and must postulate the explicit allegation of error in the legal principle applied. Such a challenge cannot be brought in connection with the mere assertion of deficiencies in investigation and reasoning, or of incorrect appreciation of the evidential findings.