Short answer. The spouse of the donor or donee. Article 739 makes a donation between persons guilty of adultery or concubinage void, and it says the action to declare it null may be brought by the spouse of the donor or the donee. The guilt can be proven by mere preponderance of evidence in that same action.
What the law says
the action for declaration of nullity may be brought by the spouse of the donor or donee; and the guilt of the donor and donee may be proved by preponderance of evidence in the same action.
Civil Code, Article 739 — Donations That Are Void. Read the full provision →
Donations the law declares void
Article 739 lists certain donations that are void from the start. Among them are donations made between persons who were guilty of adultery or concubinage at the time of the donation, donations between persons found guilty of the same criminal offense in consideration of it, and donations to a public officer or his close relatives by reason of his office. The first category exists to prevent a guilty spouse from funneling property to a partner in the affair, using a gift to reward or maintain an illicit relationship at the family's expense.
Who has standing to sue
For a donation between adulterous or concubinary partners, the article identifies who may challenge it. It provides that the action for declaration of nullity may be brought by the spouse of the donor or donee. The innocent spouse, the person most directly wronged by property being diverted to the affair, is given standing to go to court and have the donation struck down. This targets the remedy at the party with a genuine stake in undoing the gift, rather than leaving the void donation to stand for lack of anyone to contest it.
Proof by preponderance of evidence
A crucial feature is the standard of proof. The article states that the guilt of the donor and donee may be proved by preponderance of evidence in the same action. This means the innocent spouse need not first obtain a criminal conviction for adultery or concubinage. In the very civil case to void the donation, the guilt can be established by the ordinary civil standard, preponderance of evidence, which is lighter than the proof beyond reasonable doubt required in a criminal case. This makes the remedy realistically available without waiting on a separate prosecution.
What this means in practice
For a spouse who discovers that property was given to a partner in an affair, Article 739 offers a direct route. The spouse can file an action to declare the donation void and, in that same case, prove the adultery or concubinage by preponderance of evidence, without needing a prior criminal judgment. The donation, being void, conveys nothing, so a successful action returns the property to where it belongs. The practical steps are to gather evidence of both the donation and the illicit relationship and to bring the nullity action as the wronged spouse.