Michelle Arnold has answered this question several times already, that an afternoon wedding Mass on Saturday satisfies the Sunday obligation, but my question is: What if a particular bishop should say, “Not in my diocese”? To your knowledge are there any bishops who have actually said this? What is one’s obligation to investigate this if you are a guest at a wedding in another diocese?
So far as I know, no bishop has said this or would say it. That’s because canon law states:
The obligation of assisting at Mass is satisfied wherever Mass is celebrated in a Catholic rite either on a holy day itself or on the evening of the previous day (canon 1248 §1, Code of Canon Law).
Since a Catholic nuptial Mass is legitimate Catholic Mass, it qualifies for satisfying the Sunday obligaton when it is celebrated on a Saturday afternoon. There is no need to check with a bishop to ask if he has a different standard in his diocese. Only if the Vatican issued a clarification on the matter would there be an issue.