Seller v. Buyer: Unilateral Price Revision as Potestative Condition

A seller, having delivered goods, sued the buyer for payment, but the buyer raised a defense based on a contractual clause allowing unilateral price revision if market conditions changed significantly before delivery. The Court of Cassation overturned the lower court's ruling that upheld the unilateral price revision, reasoning that the clause permitting one party to unilaterally modify the price according to market fluctuations constituted a potestative condition regarding the obligation of the buyer to pay the agreed price, rendering the underlying obligation void for lack of a determined object or consideration, as the seller was not bound to accept the modified price, which violates the principle requiring a determined or determinable price in a sales contract.