In the procedure arbitration the omitted compliance of the principle of the contradictory (sanctioned by art. 816-bis, co. 1, cod. Proc. Civ., Already in priority ri Conducted in art. 816 of the Italian Civil Code civ.) not is a formal vice mai ma activity. nor consequent that, to the finical of the declaration of nullity, it is necessary ascert are the impairment of the right of defense, keeping account of the mode of the comparison between parts (having regard at respective claims) and of the chances, per le themselves, of exercise, in respect of the rule audiatur et altera pars, on a plane of equality .