The paper examines the influence of the Apostolic Letter Motu Proprio Antiqua ordinatione written by Pope Benedict XVI on the scope of the adversarial principle in the administrative litigation proceedings before the Supreme Tribunal of the Apostolic Signatura. In this context, the considerations concern the changes that the reform of Pope Benedict XVI introduced in the scope of the minimal conditions for adversarial proceedings in the analysed canonical process in relation to its elements, i.e.: complaint as a proceeding impulse, classification of the object of the process, parties of the dispute and the entity entitled to settle it, equality of the litigants, minimum disposition of the parties, an independent and impartial judicial organ. In conclusion, the 2008 reform of Pope Benedict XVI has had a significant impact on the scope of the adversarial principle in the administrative litigation proceedings in the Supreme Tribunal of the Apostolic Signatura.