I have been an apologist for Catholic Answers since 2003. When people find out how long I've been with Catholic Answers, they sometimes ask, "What is the most-asked question you receive?" That's easy: Can I go to this wedding? The question has been asked so often, in fact, that in 2007 I created a checklist for laypeople to use to decide for themselves if they could go to a particular wedding. In the years since, that checklist has become one of the most-viewed apologist Q&A's on the Catholic Answers Forums, with over 75,000 views.
Despite the dizzying variety of circumstances under which people marry, that checklist is still relevant today. It required just one substantive change in the years since, when Pope Benedict XVI ruled in his motu proprio Omnium in Mentem that a formal act of defection from the Church no longer freed a Catholic from the obligation to marry according to Catholic marital law:
The Code of Canon Law nonetheless prescribes that the faithful who have left the Church "by a formal act" are not bound by the ecclesiastical laws regarding the canonical form of marriage (cf. can. 1117), dispensation from the impediment of disparity of cult (cf. can. 1086), and the need for permission in the case of mixed marriages (cf. can. 1124). The underlying aim of this exception from the general norm of canon 11 was to ensure that marriages contracted by those members of the faithful would not be invalid due to defect of form or the impediment of disparity of cult. . . . I decree that in the same Code the following words are to be eliminated: "and has not left it by a formal act" (can. 1117); "and has not left it by means of a formal act" (can. 1086 § 1); "and has not left it by a formal act" (can. 1124).Here is the checklist, which was based in part on Should I Attend?, prepared by Catholics United for the Faith:
- Catholics may attend all presumptively valid marriages of Catholics, non-Catholics, and non-Christians.
- For Catholics marrying other Catholics or marrying a non-Catholic Christian or non-Christian, a wedding is presumptively valid if it is done in accordance with Catholic marital law. Catholics marrying non-Catholic Christians or non-Christians need the necessary canonically appropriate permissions to marry the non-Catholic party and to marry in a non-Catholic ritual (if applicable).
- For non-Catholics and non-Christians who are marrying other non-Catholics or non-Christians, a wedding can be considered presumptively valid if there are no known impediments to the marriage. The most common impediments outsiders are likely to know about are previous marriage, close blood relationship, or same-sex partners. If none of these impediments are known to exist, a prospective guest may presume that the wedding will be valid.
- The Church does not explicitly forbid Catholics from attending presumptively invalid marriages. Catholics must use their own prudential judgment in making the decision, keeping in mind the necessity to uphold the Catholic understanding of the sanctity of marriage. To make such a judgment, you might ask yourself if you believe the couple is doing the best that they can to act honorably and according to the truth that they have. For example, you might decide to attend the presumptively invalid wedding of a couple who is expecting a child (thereby attempting to provide a family for that child); but you might decline to attend the presumptively invalid wedding of a couple you know to have engaged in adultery (thereby destroying previous marriages and families).
- While there may be just reason to attend a particular wedding that will be presumptively invalid, I cannot recommend participating as a member of the wedding party in such weddings. There is a difference between attending as a non-participating guest and actively involving yourself in the wedding.
- If you are not attending the wedding as a matter of principle, then I cannot recommend attending a reception or giving a gift to honor an occasion that you believe in conscience that you cannot celebrate. I do recommend writing the couple a letter in which you express your love and prayers for them. (If prudence suggests it, it is fine to withhold from them what you will be praying to God that they obtain, such as the grace of repentance and conversion.)
- In the case of same-sex partners, the Church has spoken so strongly against "same-sex marriage" that I cannot recommend attending or celebrating "same-sex weddings" under any circumstances.
I think you are right to avoid attending this wedding. Clergy and consecrated religious are, among other things, the "public face" of the Church, so to speak, and so have to be even more careful to avoid giving scandal by appearing to approve of presumptively invalid marriages. I disagree with you only in the idea you had to send a letter rather than meet personally with your family.
It is no doubt far easier for you to counsel unrelated parishioners than it is to counsel family, but certainly your family is entitled to personal priestly counsel from you. They are free to accept or reject it, but at least you will have tried. Explain to them what constitutes a valid marriage for the Church, explain to them your own responsibility to uphold the sacrament of matrimony through your priestly ministry, and then explain that this means that you regretfully are unable to attend this wedding. Assure them of your love and prayers, and your willingness to help should they decide to do what is necessary to marry validly. Sometimes I am asked why the Church does not just tell Catholics that they cannot attend non-Catholic marriages. It would be so much easier to put the blame for not being able to attend a family member's non-Catholic wedding on the Church. I think there is wisdom though in the Church's relative silence on this matter.
One, not all marriages outside the Church are conducted under the same circumstances and it would be unjust to treat all non-Catholic marriages as if they were pressed from the same cookie cutter. Two, it forces Catholics to take responsibility for their faith. They must evaluate a given situation and make the best decision they can in charity and using prudential judgment. They must be the ones to say, "I love you, and I wish I could witness your marriage, but my conscience will not allow it."
And, finally, if Catholics carefully avoid blaming the Church for their decision, then perhaps their loved one will want to know what the Church has to say about the planned marriage—and, if so, perhaps seek to regularize their marriage so that Catholic relatives may attend in good conscience.