Is a prenuptial agreement permitted for a Catholic marriage?
Generally speaking prenuptial agreements are frowned on. They may be permitted under certain circumstances and only with the permission of the local ordinary (bishop).
Can. 1102 §1. A marriage subject to a condition about the future cannot be contracted validly.
§2. A marriage entered into subject to a condition about the past or the present is valid or not insofar as that which is subject to the condition exists or not.
§3. The condition mentioned in §2, however, cannot be placed licitly without the written permission of the local ordinary.
Fr. Ken Doyle writes along similar lines in the Catholic Times:
Then, to the matter of the prenuptial agreement: The Catholic Church does not have a blanket prohibition of “prenups.” In certain cases, they can be quite valid and helpful
When a widow marries a widower, for example, and they both have children from their previous marriages, a prenup is a legitimate way of determining what is common property and what is separate as a basis for determining the inheritance rights of each spouse’s children.
In most cases, though, prenups are a bad idea and may even call into question the validity of the marriage itself. … Clearly, the church’s teaching is that marriage is permanent and requires an unconditional commitment. Accordingly, Canon 1102 of the church’s Code of Canon Law says that “marriage subject to a condition about the future cannot be contracted validly.” For a prospective spouse to say, for example, “I will marry you, if you agree I’ll get half the assets at a divorce,” strikes at the heart of the church’s view of marriage.
The very contemplation of divorce at the outset of a marriage creates an “escape hatch” and could well imply something less than a total commitment. (Full article here)
In other words, prenups may be warranted in very specific circumstances, such as the case cited where there are pre-existing children with inheritance rights from their deceased parent. In such a case, the prenup applies irrespective of whether the couple later divorce as it is often about specifying what rightly belongs to the widowed spouse (and therefore able to be shared with the new spouse) and what belongs to the children but is perhaps held in trust.
For most couples, prenups are considered to contradict the essence of Catholic marriage as a total, permanent and unconditional commitment as they presuppose the dissolution of the marriage. As such, the presence of a prenup calls into question the validity of the marriage.
In another sense the marriage of a Catholic to a non-Catholic is a prenuptial agreement in itself:
The Catholic rite of marriage is actually a pre-nuptial agreement in itself. When one party says “I take you as my husband/wife” and the other party does the same, that nugget within the wedding ceremony is actually the contract. All the rest, Dr. Peters notes–the promise to cherish “in good times and in bad” and recitals of love and exchange of rings–those things are lovely mutual promises but are so much window dressing on the actual statement of contract contained within the ceremony. And the promise, still common today, by a non-Catholic spouse to permit any children from the marriage to be raised in the Catholic faith is another “pre-nuptial agreement.” - Can a Catholic Sign a Prenuptial Agreement?