2A. Power of court to add government or other authority as a defendant in a Suit relating to the validity of any statutory instrument.- The court may, at any stage of the proceedings in any suit involving any such question as is referred to in rule 1 A, order that the government or other authority shall be added as a defendant if the government pleader or the pleader appearing in the case for the authority which issued the instrument, as the case may be, whether upon receipt of notice under rule 1 A or otherwise, applies for such addition, and the court is satisfied that such addition is necessary or desirable for the satisfactory determination of the question. | 