A more thorough explanation:

Definition: Defense au fond en droit is a legal term used in civil law that refers to a demurrer.

Example: In a civil lawsuit, the defendant may file a defense au fond en droit, which is a motion to dismiss the case based on the legal insufficiency of the plaintiff's claim. For example, if the plaintiff fails to state a valid cause of action or if the claim is barred by the statute of limitations, the defendant may file a defense au fond en droit to have the case dismissed.

Explanation: The example illustrates how defense au fond en droit is used in civil law to challenge the legal sufficiency of a plaintiff's claim. It is a motion to dismiss the case based on the merits of the claim rather than procedural issues. The defendant argues that even if all the facts alleged by the plaintiff are true, they do not constitute a valid cause of action.