The distinction between arbitration and contractual arbitration (arbitrato irrituale) turns on the intention of the parties, directed in the first case to obtaining an award capable of being declared enforceable and of producing the effects of a judgment, and in the second to entrusting the arbitrators with the resolution of the dispute by purely contractual means, through an amicable settlement or a contractual determination attributable to the parties' own intention. For the purpose of identifying the means of challenging the award, what matters is not the nature of the arbitration stipulated by the parties, but the nature of the act actually performed by the arbitrators. In order to establish whether the arbitration is arbitration proper or contractual arbitration, the arbitration clause must be construed according to the ordinary canons of interpretation, having regard to the wording, the parties' common intention and their overall conduct, including conduct subsequent to the conclusion of the contract. Neither the description of the arbitrators as amicable compositors nor a provision that the decision is not reviewable or not appealable is symptomatic of contractual arbitration, such features being compatible with arbitration proper. The express characterisation of the arbitration as contractual (irrituale), together with a provision for a decision ex aequo et bono and without procedural formalities, unequivocally denotes the parties' intention to entrust the arbitrators with the resolution of the dispute by purely contractual means. An application to set aside before the Court of Appeal is available only in relation to arbitration proper; in the case of contractual arbitration, even where the arbitral decision has been filed and declared enforceable, such a challenge is inadmissible, the only remedy properly available being an action for defects of the contractual act, to be brought in compliance with the ordinary rules on competence and with the two-tier structure of the proceedings on the merits. An award rendered in contractual arbitration cannot acquire enforceable effect, the implementation of the rights arising from it being left exclusively to the parties' conduct. An award in contractual arbitration which settles by way of compromise the claims arising from a pre-existing relationship does not in itself remove the right from the short limitation period proper to the relationship relied upon, a novation replacing the title of the right being required for that purpose. The limitation period for the right established by the arbitrators runs from the date of the last signature of the award, the moment from which it becomes binding between the parties.