Question:
Answer:
A Catholic cannot use his or her conscience (the internal forum) to overturn a ruling of the diocesan tribunal (external forum). Canon 1671 clearly states that “marriage cases of the baptized belong to the ecclesiastical judge by proper right.” This is because “marriage is not simply a private decision,” but a public one, involving the Church, and the spouses, “both individually and as a couple.” According to the Congregation for the Doctrine of the Faith’s 1994 Letter to the Bishops Concerning the Reception of Holy Communion by the Divorced and Remarried, not to recognize the Church’s mediation in the judgment of the nullity of a previous marriage, “would mean in fact to deny that marriage is a reality of the Church, that is to say, a sacrament” (no. 8). The document goes on to say:
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. (7) In …the case of those who are subjectively certain in conscience that their previous marriage, irreparably broken, had never been valid. It must be discerned with certainty by means of the external forum established by the Church whether there is objectively such a nullity of marriage. (9)
http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_14091994_rec-holy-comm-by-divorced_en.html