Short answer. Not always on your own terms. Where the buyer took only a share of an undivided property and later came to own the whole of it because the property could not be divided and had to be sold as a unit, he can require a seller who wants to redeem to take back the entire property rather than one fraction.
What the law says
In a sale with a right to repurchase, the vendee of a part of an undivided immovable who acquires the whole thereof in the case of article 498, may compel the vendor to redeem the whole property, if the latter wishes to make use of the right of redemption.
Civil Code, Article 1611 — Redemption of a Whole Undivided Immovable. Read the full provision →
What the article is actually about
Article 1611 of the Civil Code covers a narrow but awkward situation. A person owning an undivided share of land sells that share under a right of repurchase. Later the co-ownership is brought to an end: the property cannot conveniently be divided, so it is sold as a unit, and the buyer of the share ends up holding all of it. The article then allows that buyer to compel the vendor to redeem the whole property, if the latter wishes to make use of the right of redemption. Read the condition carefully. Whether to redeem at all remains the seller's decision. What he loses is the option of redeeming only his old slice.
Why the law is arranged this way
The rule spares the buyer from being forced back into a co-ownership he never agreed to. He acquired the entire property; if the seller could take back only the original fraction, the buyer would find himself sharing the land with the very person he bought out, unable to use or dispose of it freely. Requiring an all-or-nothing choice keeps the property in one piece. It cuts the other way too, and fairly: the seller is under no obligation to redeem, so if taking back the whole property is beyond his means he may simply let the right lapse.
It bites only in that specific situation
Do not stretch the article further than it goes. It applies where the buyer of a share came to own the whole because the property was indivisible and had to be sold as a unit in the course of dissolving the co-ownership. It does not apply merely because a buyer quietly bought out the other co-owners one at a time, and it does not apply where the land can in fact be partitioned and each portion physically identified. If the property was divided and your share is a distinct piece, the ordinary rules on repurchasing what you sold govern instead.
What redeeming costs, and the clock
Redemption is neither free nor open-ended. A seller exercising the right must return the price and the further sums the law requires a redeeming seller to reimburse, including certain expenses the buyer put into the property. It must be done within the period fixed for repurchase, and that period is short; once it passes the buyer's ownership becomes absolute and no court extends it out of sympathy. Before deciding, have the property valued, read the deed to see exactly what right was reserved and for how long, and establish what has happened to the co-ownership since. Whether redeeming the whole property is worth doing is as much a financial question as a legal one.