In contracts concluded with consumers, an arbitration clause, as a clause establishing a derogation from the jurisdiction of the ordinary courts, is presumed unfair until the contrary is proved under Article 33, paragraph 2, letter t), of Legislative Decree No. 206/2005, and is therefore void under Article 36 of the same decree; it is for the professional to prove that the clause was individually negotiated, it not being sufficient that the individual clauses were read and that their content was discussed and clarified, the professional being required to show that the consumer actually exercised bargaining power in a manner that was not merely formal and had some possibility of modifying the content of the contract.