The ordinary judge, although competent to issue a payment order notwithstanding the existence of an arbitration clause in the contract from which the credit relationship originates, loses jurisdiction when in the opposition to the decree the debtor raises the defence of arbitral jurisdiction, being required to revoke the payment order and refer the dispute to the arbitral tribunal.
The question of the existence of arbitral jurisdiction constitutes a matter of jurisdiction in the technical sense and not of merit, being preliminary and absorbing with respect to every other defence articulated in the proceedings.
The judge hearing the opposition to a payment order, having found lack of jurisdiction due to the existence of an arbitration clause, must declare both the lack of jurisdiction of the judge who issued the decree and the nullity of the decree itself, ruling by judgment and not by order, given the dual content of upholding the opposition on procedural grounds and declaring the nullity of the decree.