An arbitration clause does not preclude the ordinary court from issuing a payment order (decreto ingiuntivo), since the lack of ordinary jurisdiction relates to the adjudication of disputes that presuppose adversarial proceedings, which are absent in summary payment proceedings (procedimento monitorio).
Where opposition is brought against a payment order and the debtor raises the arbitral jurisdiction, the conditions established in the arbitration agreement are satisfied, whereupon the jurisdiction of the ordinary court ceases, and the court must declare the payment order null and void and refer the dispute to arbitral adjudication.
A statutory arbitration clause that expressly provides for the lapse of arbitral jurisdiction limited to the action that has been the subject of a payment order, where the date of execution of the order precedes the perfected commencement of arbitral proceedings, establishes ordinary jurisdiction for the specific summary claim and related defences.
A counterclaim concerning matters not connected to the petitum and causa petendi underlying the summary claim remains subject to the arbitration clause and must be referred to arbitrators, even where it has been brought in opposition proceedings against a payment order that has been removed from arbitral jurisdiction.