Upvote:3
The sin of abortion carries an automatic excommunication latae sententiae," [CIC, can. 1398]. The excommunication extends to all who are involved in procuring an abortion. Abortion and the lifting of the excommunication are reserved to the local bishop or a priest authorized by the bishop may absolved the sin of abortion and lift the excommunication. It is the practice in my diocese that priests are to ask the bishop for permission for each particular case of confession of an abortion.
The following two sections of the Catechism of the Catholic Church state:
2272 Formal cooperation in an abortion constitutes a grave offense. The Church attaches the canonical penalty of excommunication to this crime against human life. "A person who procures a completed abortion incurs excommunication latae sententiae," [CIC, can. 1398] "by the very commission of the offense," [CIC, can. 1314] and subject to the conditions provided by Canon Law. [Cf. CIC, cann. 1323-1324] The Church does not thereby intend to restrict the scope of mercy. Rather, she makes clear the gravity of the crime committed, the irreparable harm done to the innocent who is put to death, as well as to the parents and the whole of society. [1463]
1463 Certain particularly grave sins incur excommunication, the most severe ecclesiastical penalty, which impedes the reception of the sacraments and the exercise of certain ecclesiastical acts, and for which absolution consequently cannot be granted, according to canon law, except by the Pope, the bishop of the place or priests authorized by them. [Cf. CIC, cann. 1331; 1354-1357; CCEO, can. 1431; 1434; 1420] In danger of death any priest, even if deprived of faculties for hearing confessions, can absolve from every sin and excommunication. [Cf. CIC, can. 976; CCEO, can. 725] [982] - THE SIN OF ABORTION AND THE SACRAMENT OF CONFESSION
Some sins and penalties are reserved to the Pope:
Normally, the bishop of the local diocese (i.e., the “Ordinary”) or his delegate is able to lift a censure such as excommunication. Some penalties, however, are “reserved to the Apostolic See,” which means they can only be lifted with special permission from the pope, generally by way of a special tribunal in Rome called the “Apostolic Penitentiary.” Offenses with this kind of reserved penalty include desecration of the blessed sacrament; physical violence against the Holy Father; a priest’s direct violation of the secrecy of the confessional; a priest’s attempt to grant sacramental absolution to his partner in sexual sin and a bishop’s ordaining another bishop without an express mandate from the Holy Father. - A Penitent’s Guide to “Reserved Sins”
Update (Thanks to Dick Harfield's comment):
Pope Francis has extended indefinitely the power of Catholic priests to forgive abortions, making the announcement in an apostolic letter released Monday (November 28, 2016). - Pope Francis extends Catholic priests' power to forgive abortion
Upvote:5
A priest can absolve any sin; however, a priest cannot absolve from reserved excommunications unless he is given permission to do so by his bishop (cf. the rite for absolving from excommunication).
Some sins (e.g., abortion; cf. Ken Graham's answer above) also incur an excommunication that is reserved to the local ordinary (bishop), and other excommunications (e.g., for illicitly consecrating bishops, as happened in China) are even reserved to the Apostolic See (pope). Thus, while a priest could absolve the sin, a bishop or pope might be necessary to absolve the excommunication (i.e., reincorporate the penitent back as a member of the Church).