Short answer. Yes. Article 1036 protects the good-faith buyer's purchase — a sale made by the excluded heir before the court's order of exclusion stays valid as to a third person who acted in good faith — but it also gives the other co-heirs the right to recover damages from the disqualified heir personally for that sale.
What the law says
Alienations of hereditary property, and acts of administration performed by the excluded heir, before the judicial order of exclusion, are valid as to the third persons who acted in good faith
Civil Code, Article 1036 — Acts Done Before the Order of Exclusion. Read the full provision →
What the law says
the co-heirs shall have a right to recover damages from the disqualified heir
Civil Code, Article 1036 — Acts Done Before the Order of Exclusion. Read the full provision →
Why the sale to an innocent buyer can still stand
Article 1036 addresses this exact timing problem. It provides that "Alienations of hereditary property, and acts of administration performed by the excluded heir, before the judicial order of exclusion, are valid as to the third persons who acted in good faith." Until a court has actually issued the order excluding the heir, that heir still appears, to an outside buyer, to have the authority to deal with the property. The law protects a buyer who relied on that appearance in good faith, rather than voiding every transaction the disqualified heir entered into before the exclusion became official.
But the co-heirs can still go after the heir directly
The same article gives the other heirs a remedy of their own, aimed not at the sale but at the person who made it: "the co-heirs shall have a right to recover damages from the disqualified heir." So while the buyer's title to the property is protected, the estate's loss does not simply disappear. The disqualified heir, who had no right to the property to begin with, remains personally answerable to the co-heirs for the value taken out of the estate through that sale.
What makes a buyer's good faith matter here
The protection for the buyer turns specifically on good faith — meaning, in essence, that the buyer did not know, and had no reason to know, that the heir selling the property was going to be excluded from the inheritance. A buyer who was aware of a pending disqualification, or who had reason to suspect the seller's right to the property was in question, is in a different position than one who dealt with the heir before any of that was apparent. Good faith is what the article's protection is built around.
The disqualified heir's personal exposure
Because the recovery under this article runs against the disqualified heir personally, rather than against the property or the buyer, the co-heirs are not left simply absorbing the loss caused by a sale that predated the exclusion order. The article does not fix a specific amount or method for calculating those damages, leaving that to be worked out based on the actual harm the estate suffered from the alienation. What it does establish clearly is that the disqualified heir cannot walk away from a sale made before exclusion without answering for it to the co-heirs.