The thing is to not look at this as a matter of “rules” but as a matter concerning the Church’s responsibilty to oppose bigamy. This is why marriages enjoy the presumption of validity. So sure, when there is a certain defect of form that can’t reasonably be disputed, maybe there is an issue of “rules” when comes to pastoral handling of these things. In that case, maybe. When there is a reasonable doubt, though, you have to say, “hey, we have to treat this as if it may be bigamy until there is no reasonable doubt that it is not.”
