The reason why it changes very little is two-fold.
First, most priests in the U.S. already have through their bishops what Pope Francis is extending to priests throughout the world: the faculty to lift the canonical penalty of excommunication from those who have had an abortion or have closely cooperated in another’s abortion, aware that such an action bears the canonical penalty of automatic excommunication.
Second, very few people who have an abortion or closely cooperate in someone’s having one incur the penalty of automatic excommunication.
A little background in canon law might be helpful to understand more fully those reasons.
If someone has incurred the penalty of automatic excommunication for the sin of abortion, before a priest can absolve that sin and all other sins, that penalty (censure) would have to be lifted. If his bishop hadn’t given him the faculty to do so, then if someone confesses the sin of abortion, he would need to figure out whether the excommunication had been incurred. If it had been, then — outside of a danger-of-death situation in which every priest has the ability to absolve of necessary censures to make absolution possible — the priest would need to ask the person to return to the confessional at a later time while he requests permission from the bishop to lift the censure so that he could then absolve the sin. A priest is trained to ask this permission in a way totally protecting the identity of the penitent if he himself even knows the penitent’s identity.
A priest occasionally has to ask for similar permission from the Vatican’s Apostolic Penitentiary for other sins so grave they likewise incur automatic penalties, like the desecration of the Eucharist, or the less frequent occurrences of someone’s trying physically to attack the Holy Father, a priest’s breaking the seal of confession or attempting to absolve an accomplice in a sin against the Sixth Commandment, or a bishop’s having ordained someone a bishop without a papal mandate.
Once a priest receives the necessary permission to absolve the censure, he can do so in the confessional and then absolve the sin.
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