5. Subject to the provisions of this Order (and, in particular, to Articles 16 and 51(2)) and to rules of court, in exercising its jurisdiction in relation to nullity of marriage the court may act and may give relief on principles and rules which, in the opinion of the court, are as nearly as may be conformable to those on which the ecclesiastical courts of Ireland acted and gave relief before 1st January 1871.N.I.