AGENTE DIPLOMATICO. — An organ of political relations between States, charged with representing, temporarily or permanently, the sending State in the State where he exercises his functions. The use of occasional and temporary embassies dates back to the most remote antiquity. It was only in the second half of the seventeenth century, however, that the practice of States exchanging permanent diplomatic representatives became general (the first permanent representation was that established by the Republic of Venice in Genoa in 1455). This practice has acquired such a general and regular character that one speaks of the active and passive right of legation as an attribute of international personality, and it is debated whether this “right” also belongs to entities other than States and the Holy See. It must nevertheless be excluded that the exchange of diplomatic agents between two States constitutes a matter of right and obligation. Diplomatic agents are distinguished as ordinary and extraordinary. This distinction places, on the one hand, envoys of a permanent character, whose task is to protect the interests of the sending State in the State where they are located, observing and reporting to their government, serving as intermediaries for communications, supervising compliance with the commitments undertaken toward their government by the foreign government, conducting negotiations, protecting resident nationals, etc.; and, on the other, envoys without a permanent character, entrusted with special missions, such as the conclusion of a treaty, the presentation of a public apology, an official proposal of marriage, etc.; or with representing the State at a congress, a conference (delegates), or an official ceremony. According to the regulations adopted at the Congress of Vienna (protocol of the session of 9 March 1815 and additional protocol of Aix-la-Chapelle of 21 November 1818), intended to put an end to questions of precedence that often gave rise to controversy, diplomatic agents are classified into four categories in order of importance: 1) ambassadors, to whom papal legates and nuncios are assimilated; 2) extraordinary envoys, plenipotentiary ministers, and internuncios; 3) resident ministers (a class added at the Congress of Aix-la-Chapelle); 4) chargés d’affaires: envoys of the first three classes accredited to the Head of State, chargés d’affaires to the minister of Foreign Affairs. According to the Vienna Regulations (art. 2), only the first category possesses representative status; but this distinction, deriving from the quality of personal representatives of the Sovereign originally attributed to ambassadors, is understood in the sense that only ambassadors represent, in addition to the State, the person of the Head of the accrediting State as well, and it is expressed solely in ceremonial prerogatives. The agents of the categories listed above are merely the heads of diplomatic representations, whose members have increased and continue to increase in number and variety of functions in step with the development of international relations. Normally, a representation consists, in addition to its head, of councillors, secretaries and attachés of legation, chancellors, and other official personnel.
Diplomatic agents accredited to a State form the diplomatic corps, at the head of which, by tradition and by express provision of the Vienna Protocol, stands the papal nuncio or the highest-ranking or most senior of the lay diplomatic agents. The sole substantive function of the diplomatic corps is to supervise respect, on the part of the local government, for the immunities and privileges belonging to its members. The diplomatic mission, a term designating the period during which the diplomatic agent exercises his functions in a State or at the Holy See, officially begins after the two States have respectively expressed the desire to send and receive the diplomatic agent, with the presentation of the letters of credence (v.), preceded, in the case of agents of the first three classes, agrément (v.), or “approval,” of the receiving State; it ends with the completion of the mission (extraordinary envoy); with the recall by the accrediting State; with the rupture of diplomatic relations; with the outbreak of a state of war between the two States; or for personal or administrative reasons resulting in the replacement of the envoy.
During the period of their stay in the accrediting State, diplomatic agents enjoy special immunities and privileges (v.) intended to facilitate the performance of their mission.