Q. 1. What does it mean to be excommunicated in the Catholic Church?
A. 1. First of all, let me tell you one thing, it is something that you do not want happening to you. There are two types of excommunications: LatŠ and FerendŠ SententiŠ.
"The first, "LatŠ SententiŠ" is incurred as soon as the offence is committed and by reason of the offence itself (eo ipso) without intervention of any ecclesiastical judge; it is recognized in the terms used by the legislator, for instance: "the culprit will be excommunicated at once, by the fact itself [statim, ipso facto]". The second, "FerendŠ SententiŠ" is indeed foreseen by the law as a penalty, but is inflicted on the culprit only by a judicial sentence; in other words, the delinquent is rather threatened than visited with the penalty, and incurs it only when the judge has summoned him before his tribunal, declared him guilty, and punished him according to the terms of the law. It is recognized when the law contains these or similar words: "under pain of excommunication"; "the culprit will be excommunicated". [Source: http://www.newadvent.org/cathen/05678a.htm]
I would like to clarify a few things regarding the application of excommunications.
Anyone involved in an abortion, incurs an automatic excommunication (FerendŠ SententiŠ). "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." (C.C.C. # 2272)"
"A person who procures a successful abortion incurs an automatic (latae sententiae) excommunication." [Code of Canon Law 1398]
This includes Presidents, Prime Ministers, politicians, all members of the government. In the case of abortion, by their action only, these persons do not need to be publicly informed that they are excommunicated. All those who suggest or pass a law that promotes abortion, are automatically excommunicated. Their excommunication does not have to be public. Their action is sufficient to incur the excommunication. Accordingly, it can be said that most ex-Catholic politicians today are among the excommunicated. They cannot be called Catholics because they no longer belong to the Catholic Church.
A teacher, who suggest abortion for whatever reason, is automatically excommunicated.
A Doctor or nurse who assists in an abortion, is automatically excommunicated.
A person who is excommunicated in the Catholic Church, cannot receive any of the Sacraments of the Catholic Church.
Therefore, a person who marries in the Catholic Church while under the punishment of a latae sententiae excommunication for partaking in an abortion, and not having had the excommunication lifted by a Bishop (or a priest to who the authority has been delegated), their marriage is not valid.
To be readmitted into the Catholic Church, you must have your excommunication lifted prior to going to Confession because you cannot validly receive any Sacraments while you are excommunicated. Your excommunication can be lifted by going to Confession to the Bishop of your Diocese or to a priest who has received the authority to lift excommunications that can only be lifted by a Bishop. When you go to confession to a priest, ask him if he has received the faculty to lift excommunications. If yes, you may then proceed with him with the details of your situation. If no, ask him to what priest you must go to confession in order to have your excommunication lifted.