In the matter of the challenge of the arbitral award, the expression "the law" contained in art. 829 co. 3 cod. proc. civ. refers to the law in force at the time of the conclusion of the arbitration agreement, with the consequence that the regime governing the challengeability of the arbitral award for breach of rules of law relating to the merits of the dispute is determined by reference to the rules applicable ratione temporis to the agreement itself.
The arbitral award cannot be challenged on the ground of errors of fact in the reconstruction of the events forming the subject-matter of the proceedings, the challenge for nullity being confined to the breach of rules of law, to the exclusion of any review of the findings of fact made by the arbitrators.
The court-appointed expert opinion ordered in arbitral proceedings does not constitute a "fact" the failure to examine which may be raised pursuant to art. 360 co. 1 n. 5 cod. proc. civ., given that the court-appointed expert opinion is an evidential instrument and not a historical fact.