The warranty against eviction is implied in every sale. Nevertheless, the parties may agree to increase or to limit the warranty. They may also agree to an exclusion of the warranty, but even in that case the seller must return the price to the buyer if eviction occurs, unless it is clear that the buyer was aware of the danger of eviction, or the buyer has declared that he was buying at his peril and risk, or the seller's obligation of returning the price has been expressly excluded.
In all those cases the seller is liable for an eviction that is occasioned by his own act, and any agreement to the contrary is null.
The buyer is subrogated to the rights in warranty of the seller against other persons, even when the warranty is excluded.