APOSTOLIC NUNCIO. — According to the present-day concept, an Apostolic Nuncio is a titular archbishop sent by the Pope as his permanent diplomatic representative to the head of a State. The functions of the nuncio are twofold: those of representing the Supreme Pontiff before the civil government, and those of representing the same Roman Pontiff before the Catholic communities existing in the State to which he is accredited. The first representation is absolutely essential to the qualification of nuncio, and it is by virtue of this that he is distinguished from the Apostolic Delegate; the second is common to both (can. 267).
As representatives of the Pope before civil governments, nuncios enjoy the rights accorded to representatives of a foreign State. They oversee relations between the Apostolic See and the governments to which they are accredited, ensuring compliance with mutual agreements by both civil and local ecclesiastical authorities, and safeguarding the prerogatives of the Church and the rights of Catholic communities. They interpret the just aspirations and legitimate grievances of these communities, conduct negotiations between the Holy See and the State, and report to the former on the progress and outcome of such negotiations. They inform the Apostolic See of the stance of political authorities, public opinion, political parties, and the press regarding the rights of the Church, and convey to governments the desires, requests, or remonstrances of the Holy See in accordance with its norms and instructions.
According to the regulations adopted at the Congress of Vienna in 1815, nuncios are equated with ambassadors (v. AGENTE DIPLOMATICO). Generally, the nuncio is also dean of the diplomatic corps.
As representatives of the Supreme Pastor before Catholic communities, nuncios perform a function identical to that of Apostolic Delegates (v.), with equal powers and duties. They must report to the Holy See (can. 267 § 1, n. 3) on the state of the Churches, that is, on the observance of ecclesiastical discipline by clergy and laity, the progress or decline of Catholic life in the country, the conditions that favor or hinder its development, and the means to promote its growth or remove obstacles. However, like Apostolic Delegates, nuncios must not and cannot substitute themselves for Ordinaries by exercising acts of jurisdiction within the dioceses of these (can. 269 § 1), unless they are vested with special faculties granted for this purpose.