For the purposes of characterising the nature of the arbitration as institutional or contractual (arbitrato irrituale), the primary interpretive criterion is the literal wording of the arbitration clause, whereas recourse to supplementary interpretive criteria under Article 1362 of the Civil Code, such as the overall conduct of the parties, is permissible only in the event of uncertainty as to the subject matter of the clause itself.
The provision in an arbitration clause that the arbitrators must decide in accordance with the rules of the Code of Civil Procedure constitutes an illustrative indication of the institutional nature of the arbitration, whereas the absence of references to decisions to be taken without formal procedural requirements or according to equity excludes characterisation as contractual arbitration (arbitrato irrituale).
In institutional arbitration, pursuant to Article 816-bis of the Code of Civil Procedure, the parties are free to regulate the conduct of the proceedings in the manner they consider most appropriate, subject to compliance with the adversarial principle, so that the failure to prescribe time limits, evidential preclusions or legal representation does not in itself indicate contractual arbitration (arbitrato irrituale).
The adversarial principle in institutional arbitration is considered to have been complied with where the parties are afforded reasonable and equivalent opportunities of defence.
An arbitral award is to be distinguished from an expert determination (perizia contrattuale) where the arbitrators do not confine themselves to ascertaining a matter of a technical nature but determine the dispute that has arisen between the parties.
The subjective characterisation attributed by the arbitrator to the arbitral procedure is not decisive for the purpose of establishing the institutional or contractual nature of the arbitration, provided the adversarial principle has been observed.