Pastoral Letters are a means of the local Bishop guiding, exhorting and giving focus and vision to his diocese and its faithful. It flows from his threefold areas of Episcopal Ordination; to sanctify, catechize and govern the diocese to which he is assigned by the Holy See. These letters draw from the earliest Church letters of the apostles to the communities that they founded, and continued to shepherd, as they went about evangelizing and spreading the good news of Jesus Christ. While the modern Pastoral Letters of Bishops do not rise to the level of those added to the canon of the New Testament, the means of providing some direct guidance and governance to the faithful of a diocese is very much an extension of that age old tradition. More than any single homily or letter or directive of a Bishop, a Pastoral Letter invites the clergy, consecrated religious and laity of the diocese to give prayerful and careful consideration to the content of the letter.

-Brian A. Lemoi
Director, Office of Evangelization and Lifelong Faith Formation
Diocese of St. Petersburg

More formally, ecclesiastical letters are publications or announcements of the organs of ecclesiastical authority, e.g. the synods, more particularly, however, of popes and bishops, addressed to the faithful in the form of letters.

Just as the popes rule the Church largely by means of letters, so also the bishops make use of letters for the administration of their dioceses. The documents issued by a bishop are divided according to their form into pastoral letters, synodal and diocesan statutes, mandates, or ordinances, or decrees, the classification depending upon whether they have been drawn up more as letters, or have been issued by a synod or the chancery.

The pastoral letters are addressed either to all the members of the diocese (litterœ pastorales) or only to the clergy, in this case generally in Latin (litterœ encyclicœ). The mandates, decrees, or ordinances are issued either by the bishop himself or by one of his officials. The synodal statutes are ordinances issued by the bishop at the diocesan synod, with the advice, but in no way with the legislative co-operation, of the diocesan clergy. The diocesan statutes, regularly speaking, are those episcopal ordinances which, because they refer to more weighty matters, are prepared with the obligatory or facultative co-operation of the cathedral chapter.

In order to have legal force the episcopal documents must be published in a suitable manner and according to usage. Civil laws by which episcopal and also papal documents have to receive the approval of the State before they can be published are irrational and out of date.”

Excerpted from the online version of the Catholic Encyclopedia. For more information, visit: http://www.newadvent.org/cathen/09202a.htm