After a number of interesting conversations here on CAF, I thought it would be good to post the following description of the authority of tribunals to declare marriages valid or invalid.
The Church uses its supreme authority to obligate Catholics in numerous ways beyond what merely Divine law enjoins, such as the confession of sins once a year, the Sunday obligation, and so on. These two obligations bind under pain of sin. There are exceptions to the examples I gave, because they are “positive” laws - laws which tell one to DO something rather than NOT do something. A negative law is something which forbids some behavior or act. There are some negative laws of the Church which contain explicit and implicit exceptions, such as fasting and abstinence (a very complex topic - perhaps this could even be characterized as a positive law, seeing as it is “abstinence” and “fasting” which are enjoined, rather than those things being defined by the law itself), or the age requirement for ordination. However, the latter also has an explicit “no exception exception” (see c. 1031 s. 4), the violation of which would certainly constitute sin. An example of a gravely important negative ecclesiastical law resting immediately upon Divine law, which admits of no exceptions, is the consecration of a bishop without the approval of the Holy See… This constitutes a schismatic act.
Another example of a grave negative ecclesiastical law resting on Divine law regards the usurpation of a tribunal or contradiction of a negative decision of a tribunal in the case of a declaration of nullity of a prior bond. This constitutes two acts - one a rupture of the order of law (vigilantism), the other its consummation, which is adultery: the only possible (possible!) exception could be that of a person in what is called a “conflict marriage,” where there is no objective evidence to bring before a tribunal (tribunals do not exist to serve this function… for more, see Dr. Ed Peter’s post here: canonlawblog.wordpress.com/2015/11/20/toward-informed-discussion-of-the-internal-forum/ ).
Let us see what the Catechism says on declarations of nullity:
1629 For this reason (or for other reasons that render the marriage null and void) the Church, after an examination of the situation by the competent ecclesiastical tribunal, can declare the nullity of a marriage, i.e., that the marriage never existed. In this case the contracting parties are free to marry, provided the natural obligations of a previous union are discharged.
We can see that the CCC points out that it is “the Church,” in “the competent ecclesiastical tribunal,” who can do this. The Church provides this mechanism for the simple reason that it must be used to obtain the effect of a declaration of nullity, dispensing one from the obligations which came with a public vow which by its nature has enormously important repercussions for both of the individuals contracting it and the community in which they live. As with all such public, solemn vows, we may not dispense ourselves from them.
We should note that the Church understands its authority to preside over cases of disputed validity of marriages with respect to Catholics to reside exclusively within the competent ecclesiastical forum, called a tribunal (c. 1075 s. 2, c. 1401, c. 1671). Recall that lack of canonical form is also an invalidating character of an attempted marriage: one may not excuse himself/herself from this law, but rather, the appropriate authority must be approached for a dispensation. These attempted marriages really are invalid without it. (Let us also note here that there are cases of invincible ignorance, of ecclesiastical law and of the facts of the matter, which introduces the division between material and formal sin – even though they are invalidly married, this knowledge is not available to them. Radical sanation provides a solution to such cases. But we should always presume that sane, baptized adults have the Divine law available to them, as it is written on their hearts - they are not invincibly ignorant of the right meaning of the 6th Commandment in its basic application by Christ, which is not to divorce and remarry. They must obtain sufficient certainty they are not bound to the prior bond of a baptized person still living. That certainty, the Church says, comes from the competent forum.)
It has been pointed out repeatedly in prior discussions that tribunals can make mistakes. I don’t think anybody disputes this, but nobody has shown that this would allow a petitioner to presume to usurp and/or contradict a tribunal in favor of his/her own will, to the detriment of the rights of the one in the prior union and also with possible grave scandal given to the faithful. If a tribunal makes a decision in favor of the prior union, then it must be treated as binding. But let us imagine a possible case where the so-called “internal forum solution” (or “Kasper Proposal”) is applied.