In the procedure arbitration the omitted observance of the principle of the contradictory (sanctioned by art. 816-bis, co. 1, cod. Proc. Civ., And already in precedence ric Ondotto in art. 816 of the Italian Civil Code civ.) not is a formal vice vice, ma activity. nor it follows which, to the finical of the declaration of nullity, it is necessary ascertain the concrete impairment of the right of defense, keeping account of the mode of the comparison between the parts (having about at respective claims) of the pos SIBLIBILE, per le themselves, of exercise, in respect of the rule audiatur et altera pars, on a floor of equality the faculties procedural them attributed.