There’s a lot of combinations of sacramental debates happening today, but most of them are very similar:  Someone’s Catholic family member is getting married outside the Church.  Half the family feels squeamish about it.  A priest steps in and says to the more conservative family members, “You should indeed go to your son’s wedding outside the Church, so as to not break the bonds of charity.  That way, you can evangelize him back into the Church later.” Then, all the lay people in the family have their consciences euthanized by the smiling priest, and they all go to the “wedding.”

Here’s why that priest is wrong and it’s actually a mortal sin to go to the “wedding” of an ex-Catholic getting married outside the Catholic Church:  A true marriage is a sacrament.  A simulation of a sacrament is an “imitation-mockery” of a sacrament.  Not only would attending an ex-Catholic’s “wedding” outside the Church be an invalid sacrament, but it would be a simulation of a sacrament.  Simulation is a canonical term meaning “imitation” or “mockery.”

Would you go to a “mockery Mass” by a non-Catholic Wiccan family-member just because you were requested there with pleading tears?  Would you confess your sins in an “imitation-confession” to a Methodist minister?  Would you have your comatose Italian Catholic grandmother receive extreme-unction from an Episcopalian priestess-chaplain at the local city-hospital for “pastoral reasons”?  Of course, you understand that participation in any such mockery of a Catholic sacrament would probably be a mortal sin, even if you were simply a side-participant in it.

Why then would you participate in the simulation of the great sacrament of Matrimony?  Getting married outside the Catholic Church is a mortal sin for a baptized Catholic.  If you encourage another’s mortal sin, you obviously place yourself in mortal sin, too. Every Catholic knew this 100 years ago.  Remember that the traditional Magisterium of the Catholic Church listed nine ways to being an accessory to another’s sin:

1. By counsel
2. By command
3. By consent
4. By provocation
5. By praise or flattery
6. By concealment
7. By partaking
8. By silence
9. By defense of the ill done.

Therefore, attending an ex-Catholic’s attempted-wedding outside the Catholic Church would make you an accomplice in another’s mortal sin by consent, by praise, by partaking and by silence.  (See numbers 3, 5, 7 and 8 above.)   That is, unless you’re going to stand up at the fake-wedding and scream and try to stop such a farce, silence at such an event makes you nearly as guilty as the fiancés executing such an invalid simulation of a sacrament.

Or don’t you believe Matrimony to be a Holy Sacrament of the Catholic Church?

Another part of classic morality that most priests hide from their lay people is that for an ethical decision to be moral, all three of the following items must be morally good:
1) the object (deed) and
2) the intention and
3) the circumstances.

If even one of those is missing from the proposed act, the traditional Magisterium teaches that the whole act is bad: Bonum ex causa integer; malum ex quocumque defectu.  Therefore, having a good intention to “win your daughter back to the Catholic Church” by attending her invalid “wedding” outside the Church will not only backfire (these things never work because adult children then see their parents’ religion as a joke to them when they don’t stick to their guns on conviction) but it’s also an offense against God.  Even if the intention part is good (“keeping the the bonds of charity with your adult child”) the object (or deed) remains evil.  Again,  malum ex quocumque defectu:  If one of the three aspects of a moral act (object, circumstance, intention) is defective, the whole shebang is rotten. It doesn’t matter how good your intention is.

A totally different question may be tackled here:  Can Catholics attend non-Catholics’ weddings who were never Catholic?   The Church recognizes the natural marriage of non-Catholics getting married outside the Catholic Church, even if she doesn’t recognize the sacramental marriage of a non-Catholic couple.  There is some debate as to whether baptized Protestants (who were never Catholic) effect the sacramental bond of Holy Matrimony.  That debate aside, I spoke to a traditional Catholic with a PhD on the topic of Catholics attending other religion’s weddings.  We are open to correction on this point, but we came to the conclusion that is probably morally acceptable for lay Catholics (not clergy) to attend the weddings of Eastern Orthodox, Protestants or Jews and maybe even secular services, with the proviso that neither fiancé(e) was ever Catholic.  Keep in mind a Catholic may never engage verbally in any liturgical prayer of non-Catholic sects, whether that setting be a wedding or anything else.  1

Going even deeper into caution, we must remember that some religions (like Hinduism) are demon-worship.  (Omnes dii gentium daemonia.—Ps 95:5)  Therefore, I would advise against Catholics attending pagan weddings even if neither fiancé(e) was an ex-Catholic, even if the Catholic layman had a resolution to refrain from their public prayer.  You don’t want to even expose yourself to pagan-worship rituals.

Two follow up notes:  1)  My friend Leila Miller is also discussing this topic of non-Catholic weddings in some recent videos on her new YT channel.  2) If this blog post leads you to confession and the priest in the box says back to you, “That’s not a sin that you attended an ex-Catholic’s wedding outside the Church,” just say “Please, Father, respect my conscience, that I need to confess this.”  (In other words, appeal to the only thing that matters to a modernist:  subjective conscience, not Church teaching.)