To clarify concepts, the external forum is the forum of public acts observable by others. In this forum, for example, a couple are married in the Church before a priest or deacon and two witnesses and they are deemed to be validly married until such time as one of the spouses dies or the marriage is declared null by a Church tribunal.
The internal forum is the forum of a person’s conscience before God and the Church. For example, it is the forum of the sacrament of penance. The acts here are not publicly known by others. In this forum a person may be convinced in conscience that their previous marriage was null for some reason, even though it was not declared null by a Church tribunal, either because the case was never taken to a tribunal or because the tribunal found that the marriage was valid.
Can people in this situation who are now in a new relationship with another person, either “married” civilly or in a de facto relationship, receive Communion?
There are a number of considerations to be borne in mind. The first and most important one is that since their irregular marriage situation is publicly known by at least some people in the parish, it would give scandal if they were to receive Communion. That is, since they are married only civilly, not in the Church, or they are in a de facto relationship, they are in the same situation as anyone else who is married civilly or in a de facto relationship and everyone knows they are considered to be “living in sin” and should not receive Communion.
The fact that they consider in conscience that their first marriage was null is not sufficient reason to receive Communion. Their first marriage was celebrated in the public forum and its nullity or validity should also be declared in that forum. Only in this way can pastors and other parishioners have security about their situation.
But can’t they make a personal judgment about the nullity of their first marriage? Since time immemorial it is a premise of the judicial system of both Church and state that no one is a good judge in their own case. Cases are always referred to third persons to be judged since these persons are considered to be impartial. For this reason we have tribunals.
But couldn’t the couple come to a judgment about the validity of their first marriage with the help of their pastor? Their pastor is usually not an expert in the canon law of marriage and he has not heard the evidence of the other party to the marriage and so cannot make a valid judgment. What is more, he too may be biased in favour of the couple. If he is an expert in canon law he will be the first one to say that the case needs to be judged by a Church tribunal.
To facilitate this judgment, in 2015 Pope Francis streamlined the judicial system for marriage cases to make it more accessible and to speed up the process. No longer is there required a second judgment by an appeals tribunal to confirm the judgment of the first tribunal, so that the whole process should ordinarily take no longer than a year. In addition, there is now a shorter process, to be judged by the bishop himself, when there are obvious grounds for nullity. This process may take as little as a few months.
So if a person is convinced in conscience that their first marriage was null they should take the case to a tribunal and have it judged by the Church. If they have already done so and the tribunal found the marriage to be valid, they have no choice but to accept that judgment.
So no, we cannot allow a couple to make a personal judgment about the nullity of their marriage. Marriage is a public state and we need security in the external forum about who is married and who is not. For this reason we have tribunals. If the tribunal finds that a person’s first marriage was valid, the couple can always be helped to live “as brother and sister” and to be forgiven in the sacrament of Penance if they fail.