The recognised right to maintain a construction or use in compliance before the coming into force of a new law or regulation. Thus, despite the the new legal framework prohibiting what was once permitted, the construction or use does not become derogatory, because of the existence of an acquired right. This right is attached to the property and not to the owner. In addition, there may be forfeiture or loss of acquired rights for various causes such as a change of use, non-use or partial or total destruction of the immovable.