Many years ago we assisted at a hybrid wedding. The groom was Prot, and the bride NO Catholic. What a disaster...the Catholic priest consecrated the Bread, the Prot minister did the Wine. !
Let's just say it was an uncomfortable ceremony, shall we?
How about weddings in front of a Justice of the Peace?
A neoS spx faithful asked the priest if he could be part of the "Wedding Party", for a ceremony in front of a Justice of the Peace. Spouses have no religion I presume. The priest gave permission...?
But the grave distinction is "assist" [party of the five, or participation], or attend ( simply being present). Sorry I don't have more details today, but eventually. Anyway, smells scandalous, sinful.