A clause providing for the non-appealability of a contractual arbitration award (arbitrato irrituale) does not preclude challenge on grounds of defects that may affect contractual intention, including breach of an essential and peremptory time limit established by the parties for the rendering of the award.
In contractual arbitration (arbitrato irrituale), breach of the time limit for rendering the award may constitute an excess of the limits of the mandate, unless it emerges unequivocally from the agreement that the parties attributed to the time limit a merely indicative value.
Where the parties agree to a time limit for rendering the award anchored exclusively to the completion of the "final submissions" and do not fix a definite time limit, the arbitrator's remission of the case for further proceedings for the purpose of obtaining court-appointed technical expert evidence does not constitute a breach of the time limit nor an excess of the limits of the mandate.
The remission of an arbitral case for further proceedings for the purpose of obtaining court-appointed technical expert evidence falls within the exercise of the arbitrator's powers under Article 816-ter of the Code of Civil Procedure, and has as a mere indirect effect that rejoinder pleadings already filed no longer constitute the "final submissions" of the proceedings.