This morning I was reading the Code of Canon Law at breakfast — there is a reason — and found my way to the rules for absolving whomsoever the priest may have screwed. This is a big no no, as the commentary explains: “the absolution of a partner in sin against the sixth commandment of the Decalogue is invalid except in danger of death”; apart from that danger, any priest who knowingly attempts to absolve an accomplice in such a sin commits a very serious offence”
One see that giving the priest the right to absolve his mistress or concubine must be strictly forbidden because it would eviscerate the requirement of celibacy. So far so obvious. But there is fascinating pendant in my commentary which says the Canon must be interpreted strictly, so no offence is committed … if the priest absolves the accomplice without in any way realising that he or she was in fact his accomplice [or] if the priest does not specifically recognise the accomplice or has doubts concerning his or her identity”
I think this deserves to be generally known as the cottaging clause, though obviously it also covers participation in masked orgies.