Remarriage. As noted above in the citation from the Catechism 2382, a ratified and consummated Christian marriage is indissoluble. This is a marriage where the vows are exchanged by two baptized persons, with the proper intention, and consummated by sexual intercourse. No power on earth can declare such a marriage null and the parties free to remarry. However, a marriage tribunal of the Catholic Church is empowered to judge whether a marriage actually did occur and to issue a Decree of Nullity (popularly, but wrongly, called an annulment) when it judges it did not. (See: Annulment/Decree of Nullity) A person who receives a Decree of Nullity is free to marry in the Church since the first marriage was defective from its beginning (i.e. no marriage). A person who remarries in the Church after an annulment is free to receive the sacraments under the usual conditions (as noted above).
However, often times individuals or couples who have remarried but without a Decree of Nullity want to come into the Church, or if already Catholic approach the sacraments of Penance and Eucharist. Sometimes they are even told they can judge these matters in their own conscience without going to a Marriage Tribunal (sometimes called “the internal forum solution”).
In “Concerning the Reception of Holy Communion by Divorced-and-Remarried Members of the Faithful” the Congregation for the Doctrine of the Faith in a letter to the world’s bishops on October 14, 1994 said,
7. The mistaken conviction of a divorced-and-remarried person that he may receive holy communion normally presupposes that personal conscience is considered in the final analysis to be able, on the basis of one’s own convictions, to come to a decision about the existence or absence of a previous marriage and the value of the new union. However, such a position is inadmissible. Marriage, in fact, both because it is the image of the spousal relationship between Christ and his church as well as the fundamental core and an important factor in the life of civil society, is essentially a public reality. [library/curia/cdfdivor.txt