Contractual arbitration (arbitrato irrituale), whereby the parties entrust a third party with the resolution of disputes through a contractual instrument referable to their will, is validly constituted when the contracting parties declare their commitment to consider the award as final and binding, equivalent to a concluded contract expressing their own personal will, subject to the observance of the adversarial principle.
A contractual arbitration award may be challenged for essential mistake only when the formation of the arbitrators' will has been deviated by an altered perception or a false representation of reality and of the factual elements submitted to their examination (mistake of fact), and not when the deviation relates to the assessment of a reality whose elements have been correctly perceived (error of judgment), with the consequence that a contractual arbitration award is not challengeable for errors in iudicando.
In relation to contractual arbitration (arbitrato irrituale), the erroneous application of the rules of contractual interpretation in construing the arbitration clause does not constitute a defect denounceable as such, being capable of assuming relevance only where it constitutes an abuse or an exceeding of the limits of the mandate conferred upon the arbitrator.