I assume that validly assisting also refers to the validity of the marriage, since a Catholic needs to be married in the presence of a witness from the Church who has jurisdiction to do so.
Dear JMKC,
If you are really concerned about that (and you should be - it is the validity of your marriage in jeopardy), you should consider getting married at your fiancée’s parish. From what I read in your previous posts, you have no doubt about her being Eastern Catholic. In interritual marriages, for validity sake, you may marry in the presence of her priest, or in the presence of your priest. If you are not sure who is the priest who has jurisdictional power over you, why not go to her priest and get married over there? This way you would eliminate any doubts on validity.
This is exactly what happened to me. I’m Eastern, my wife is Latin. We got married at a Latin rite ceremony. This possibility is explained by no less than Bishop Dimitri Salachas, a great Canon Law expert specialized in Eastern Canon Law. He is also the head of the tiny Greek-Byzantine Catholic Church sui iuris in Greece and he worked for many years in the Congregation for Eastern Churches.
For a valid marriage in the presence of her parish priest, there is no need for any faculties or delegations from your pastor. Remember, this is an interritual marriage - there is no need for a double consent, just one consent coming from one pastor is enough. Again, that is exactly what happened to me, and I work with Canon Law. I would not let my own marriage become null because of this. Back then, I did my homework and I checked all the Canon Law books prior to the ceremony.
Even if you insist in getting married in the Latin rite, though you are afraid that you’re not Latin, you would have the benefit of doubt in your favor. Since it seems impossible to ascertain for sure whether you are Latin or not (but it seems that you indeed are Latin), this is one of the cases in which the Church would supply the jurisdiction that might be lacking (supplied jurisdiction). Let’s have a look at canons 144 and 1.111, §1 of the Code of Canon Law (1983):
Can. 144 §1. In factual or legal common error
and in positive and probable doubt of law or of fact, the Church supplies executive power of governance for both the external and internal forum.
§2.
The same norm is applied to the faculties mentioned in cann. 882, 883, 966, and
1111, §1.
Can. 1111 §1. As long as they hold office validly, the local ordinary and the pastor can delegate to priests and deacons the faculty, even a general one, of assisting at marriages within the limits of their territory.
Taking away the mention of deacons for your case (your wife-to-be is Eastern for sure, she must not be married by a deacon), can you see how these two canons (144 and 1.111) would work together to make your marriage valid, even though you do not know for sure if you are Latin? There is a probable doubt about the whole theme of your adscription to a certain Church sui iuris; the most probable possibility is that you are Latin, in which case you could get married in the Latin rite without delegation by the Eastern pastor. But even if you are not Latin, since you cannot know for sure what is your Church sui iuris, the Church would supply the lacking jurisdiction and you would be validly married.
My suggestion: either marry at her parish, with the presence of her pastor (or some other priest delegated by him), or marry at the Latin rite, having the firm belief that “Ecclesia supplet” (
Church supplies the jurisdiction that maybe lacking). Do not worry about that so much, and enjoy the ceremony!