In the eyes of the Church, until an annulment is adjudicated, the divorced party is still married and thus has an impediment preventing a valid wedding. Regardless of relationship one might have to the person(s) getting married - to be in attendance at such implies support for the non-sacramental celebration. It is also, in the eyes of the Church and Divine Law, an adulterous relationship which you would be consenting to.
Do you "cut off" this person completely? No! You cannot show support for the non-sacramental union, but visiting them and/or them visiting you and/or a family get together does not necessarily imply support for their decision to "get married" outside the Church.
One would hope too that the person(s) getting married would understand why faithful Catholics cannot attend such a ceremony. It is not because they do not care, quite the opposite! They do not show because they DO care about not only the souls of those participating in the ceremony, but also those who of weaker faith which might be also in attendance and believe that your "showing up" is a sign of support.
We must pray for those caught up in such a situation which is, unfortunately, becoming all the more prevalent in today's society. Pray that they reconcile themselves before God and the Church.
To show this is not just "me" talking, here's some more references/reading for you too:
Luke16:18 (Divine Law):
“Everyone who divorces his wife and marries another commits adultery, and he who marries a woman divorced from her husband commits adultery."This same question is answered on the website of Our Sunday Visitor:
“Remarriage of a divorced person without annulment.” Invalid. Potentially remediable through annulment and sanatio (from the Latin for “healing”), which cannot be presumed. For purposes of clarity, an annulment invalidates a marriage, while sanatio validates a marriage. Practicing Catholics should not attend. Possibly against natural law; certainly does not fulfill canon law.
Because of the strong words of Jesus cited above (see Mt 19:9), I don’t see how a practicing Catholic in good conscience can attend a wedding ceremony that he knows will be an invalid marriage. His/her attendance seems to condone what is going on. Rather, he should explain to the individauls that he loves them and prays for them and wants the very best for them, but that he will not be helping them at all if he ignores the clear teachings of Jesus Christ. These can be very hard conversations. But remember what Jesus said: “Everyone who acknowledges me before others I will acknowledge before my heavenly Father” (Mt 10:32). That should be some consolation.
http://www.osv.com/tabid/7631/itemid/9254/May-I-Attend-the-Wedding.aspx
Here is what Jimmy Akin says in his article Can You Attend the Wedding?:
"I take a strict line on attending weddings that are presumptively invalid. I never advise people to go to those because of the signal it will send to the participants–and others."
http://jimmyakin.com/2012/08/can-you-attend-the-catholic-wedding-of-a-non-practicing-catholic.html
More from Jimmy Akin:
A reader writes:
What are our responsibilities as parents. I know that we cannot "celebrate" the wedding in any way so as not to lend our presence to the ceremony and thereby indicate that it is "OK", but surely if we visit the couple at any time during their invalid marriage we would be implying that it is ok? Does this mean we must no longer see our son?
The question of how to navigate social relationships without endorsing an invalid union is a very difficult question that many find themselves in. It is particularly painful and complex and depends in significant measures on how the parties are related to each other and how they would "read" different actions as messages saying things about the union.
Attending the wedding, celebrating anniversaries, letting two people share the same bed under your roof, etc., would all be actions that in our culture would be taken as an endorsement of the union. (And it is hard to see how they might be anything other than that, even in other cultures.)
However, social interactions not directly related to marriage may not be taken this way. For example, inviting people (who know that you don’t think that they are married) over to your house or going over to their house is often not read as an endorsement of a union in our culture. The act is remote enough from the marriage itself that in the opinion of many it is not necessary to refrain from these social interactions.
It most definitely is not necessary that you cut off all contact with your son. Indeed, maintaining contact with him may be essential to the future rectification of his situation. The difficult and painful thing is figuring out how to maintain contact in a way that does not send him false messages. Ultimately, one just has to do the best one can to muddle through that.On Catholic Answers:
http://jimmyakin.com/2005/08/son_planning_in.html
Am I right to refrain from attending the Episcopalian wedding of a divorced Catholic whose first marriage has not been annulled?From "All Experts" website:
You are correct. To enter into an invalid marriage simply to have a fancy church wedding because of reasons of convenience is sinful and betrays a lack of good judgment. It can also give scandal to those who are not knowledgeable in their Catholic faith.
Answered by: Fr. Vincent Serpa O.P.
http://www.catholic.com/quickquestions/am-i-right-to-refrain-from-attending-the-episcopalian-wedding-of-a-divorced-catholic-
Expert: Fr. Timothy Johnson - 2/17/2010
Question: Hello, Father. I am trying to decide if I may attend a wedding of a divorced Catholic relative. The wedding will be officiated by a Protestant minister in a residence and followed by a reception.
Answer: Hi, John:It seems to me that your presence at this wedding would be an outward sign of approval that a Catholic can just dissolve a marriage, without regard for looking at the matter of whether or not it was ever truly a sacramental marriage. It saddens me how so many Protestant ministers promote the idea that adultery and forgiveness for that adultery can dissolve a marriage bond. I have always thought that there idea of divorce and remarriage is a lot like: Find the new person who you want for your spouse, then break off with the first spouse, ask God to forgive you of your sins, and this will dissolve the marriage bond, and then you can go on to marry whomever you wish. If there is truly something more to the matter, then no Protestant has ever clearly presented to me. Personally I would not attend the wedding, but I am not you; and I can't very well force you one way or other over the internet.
Fr. Timothy Johnson
http://en.allexperts.com/q/Catholics-955/2010/2/Attending-Marriage-Divorced-Catholic.htm
Canon Law:
Canon 1059 The marriage of Catholics, even if only one party is baptized is governed not only by Divine Law but also by Canon Law, without prejudice to the competence of the civil authority in respect of the merely civil effects of the marriage.
Canon 1066 Before a marriage takes place, it must be established that nothing stands in the way of its valid and lawful celebration.
Canon 1069 Before the celebration of a marriage, all the faithful are bound to reveal to the parish priest or the local Ordinary such impediments as they may know about.
Canon 1070 If someone other than the parish priest whose function it is to assist at the marriage has made the investigations, he is by an authentic document to inform that parish priest of the outcome of these enquiries as soon as possible.
