[quote="garysibio, post:3, topic:334250"]
I was under the impression that, although 99.99999999% of the time, a priest or deacon officiates, it's not necessary. The (rather bizarre) example I heard was about a couple stranded on a desert island with no priest. They could still get married even though there was no one else there.
I thought that once a priest was validly ordained, nothing could strip him of the gifts associated with his ordination. For example, he could still confect (I think that's the right word) the Eucharist. If he can still do that, why not marriage. I know I'm missing something here. I just don't know what.
Canon law is clear (both CIC and CCEO) that two witnesses are required as a minimum. Further, for faithful of the eastern churches in union, the sacramental marriage exists, but the sacrament is incomplete, without the priestly blessing.
There is a difference between the gifts of ordination and the permission to use them. And only four sacraments are predicated upon ordination: ordination, confection of the eucharist, absolution, and confirmation/chrismation.
Ordination to the diaconate confers an indelible mark upon the soul, and the ability to give blessings, but that ability is not always permitted to be used.
Ordination to the presbyterate confers another indelible mark upon the soul, and the ability to confirm, to absolve sins, to confect the eucharist, and to perform extreme unction. All of these require unity to the church, through an ordinary†, to be used licitly, and the permission of the bishop is required.
Ordination to the episcopate confers a third indelible mark upon the soul, and the ability to ordain. The authority to ordain is restricted to a bishop-ordinary, or another bishop delegated by another ordinary. (Yes, an auxiliary bishop can ordain men for an ordinary on the authority of the ordinary and the ordination of the bishop.)
It is normal for deacons in the Roman Church to be granted the faculty (permission to use the power) of blessing, while it is rare for them to be granted it within the other 20+ churches in union with Rome.
It is normal for priests to be granted the faculty of confection of the Eucharist, to give extreme unction, and to bless, so much so that people forget all three are revokable faculties. It is uncommon for priests of the Roman Church to be granted the faculty to chrismate, but normal in the East. It is not rare for priests to be granted the faculty to hear confessions within the diocese, but it's not automatic; all priests have the faculty, by the law itself, even if all other faculties are suspended, to hear the confession of a dying person.
To witness a marriage in the name of the Church is a faculty, but one that is sometimes granted to laity, and not predicated upon ordination. It is a duty of pastors, as much as it is a faculty of pastors, and even other priests in a parish must obtain permission to do so from either the pastor or the bishop.
To baptize requires no faculty at all, other than the correct mindset, correct process, and a willing person being baptized.
To enter the religious life requires an ordinary's permission, and a priest's blessing; the priest need not be part of the order, but the ordinary needs to be. And it's normal for them to be the witness, but in a pinch, they can delegate that to another member of that community.
† Remembering that "ordinary" is canon-law for lawfully in charge of a group of the faithful and having the authority to grant faculties. An ordinary need not even be a cleric. All dioceses' bishops are ordinaries, auxiliary bishops are not. The head of an order of monks or friars is an ordinary; so is an abbot of a given monastery, or the superior of certain established houses of friars or cenobites.