Comparison between the English and the French system of the transfer of title by non–owner
The Common law system is governed by one rule: “memo dat quod non habet” (no one can give what he does not have). This means that a buyer can only get good title if he buys from the owner of the good. Common Law itself and several statutes have created exceptions to that general rule. French law is based on a whole different system. Even if the Article 1599 of the Civil Code states that the sale of a thing belonging to another is void, the Civil Code says that they are several ways to get a good title, not only by buying the good from its owner. French Property law distinguishes two notions: property and possession.
This principle is based on the théorie de l’apparence (appearance theory). This theory protects the person who, due to the circumstances, thought in good faith that a state of affair was true and acted on it. In that case, we will attach to the situation the legal effects it would have if the appearance was true. When we compare both systems, we can see that all the cases where the buyer from the non-owner can get a good title are linked to appearance. With estoppel for example, the buyer makes it look like the seller was authorized to sell. At the first look, we could think that they are fundamentally different but in the end they are based on the same considerations: law tries to protect the innocent third party who genuinely thought that the person from whom she was buying the good had the authority to sell it.