dimond

I answer that, Anyone can absolve from minorexcommunication who can absolve from the sin of participation in the sin of another. But in the case of a major excommunication, this is pronounced either by ajudge, and then he who pronounced sentence or his superior can absolve--or it is pronounced by law, and then the bishop or even a priest can absolve except in the six cases which the Pope, who is the maker of laws, reservesto himself: the first is the case of a man who lays hands on a cleric or a religious; the second is of one who breaks into a church and is denounced for so doing; the third is of theman who sets fire to a church and is denounced for thedeed; the fourth is of one who knowingly communicates in the Divine worship with those whom the Pope hasexcommunicated by name; the fifth is the case of one who tampers with the letters of the Holy See; the sixth is the case of one who communicates in a crime of one who isexcommunicated. For he should not be absolved except by the person who excommunicated him, even though he be not subject to him, unless, by reason of the difficulty of appearing before him, he be absolved by the bishop or by his own priest, after binding himself by oath to submit to the command of the judge who pronounced theexcommunication on him.

http://www.newadvent.org/summa/5024.htm