And now, back at my PC.
OneShot, I'm trying to use period documents (hence the Decretal, which is about 1140), but rather than me just post a wall of the Decretal, can we look through a relevant case? It must be I'm not understanding you.
Causus 28, OK?
If you're a Christian, and you marry a Jew, and the Jew does not convert, you are married (that is, it is a valid marriage) but it is not licit, and so therefore you must live separately, rather than as a couple,and you cannot remarry until their death. This is the church law: the secular law was that you'd be fined (up to put to death if you were in bits of Spain).
You are, in this case, married, and yet your marriage is not one which leads to the things of marriage (children, consolation, community) unless the Jew converts. Technically, you are only allowed to marry (theologically, not secularly) on the basis that they have given an oath that they will convert, but if they were lying, that doesn't dissolve the marriage. You need to do penance afterward, because you have broken the laws of the church.
So, how do you get from there, where the marriages of unbelievers are valid, but not licit or sacred, and therefore require strict separation from Catholics, to the point where a person gets to marry, and have sexual intimacy, with a dragon?
Your argument seems to be that marriage is a predating institution, but as Aquinas notes, it's from the earliest states of man. You're once again ignoring that the dragon is a dragon, not a man. If your point is you can have a de jure marriage in secular law in places where people are allowed to marry dragons,I agree, but the question was, I thought, the view of the Church?
Doctrinally, you need to push your dragon a long way to get it within the realm of the Church's approval for betrothal. Even if you assume that the dragon is a person, with all of the required attributes of a potential spouse (opposite sex, humanity, a soul, the ability to perform sacraments, the capacity to consent, having told the spouse they are a dragon, openness to the bearing of children) you still hit the point that you aren't allowed, by the order of the Pope, to marry unbaptised people lacking a firm oath of conversion. You haven't been allowed to for about a hundred years. So, is this a baptised dragon? I mean, technically we have a draconic abbot...so, sure, if you are having a fervently Catholic dragon...that gets over that hurdle. It just seems a reach.
You have quoted a lot about the previous dispensations - but seem to still fall back to the earliest one, if I'm reading your argument, rather than seeing them as superseding each other?
In ancient times, people did A, under the early prophets they did B, now they do C is an argument against doing A and B, not permission to do them. Or am I missing your point? The Church is very clear that just because people did a thing in the Bible doesn't mean you are allowed to do it now. For example, having multiple wives, and marrying your close blood kin were allowed back in Ancient Israel. It's not allowed now.
Is your argument that the grace of the sacrament makes good the deficiency of the spouse in this case, hence your highlights? My counter to that would be a person does not become a spouse, and have the grace imparted, if one is not a candidate for the sacrament. Much as ordination, in period, cannot make women priests, baptism cannot make cats Catholic, and unction cannot speed trees to Heaven. If even angels can't perform sacraments, why should dragons?