189. When the purpose of the forced intervention is to call a third person in warranty, the warranty is termed simple if the plaintiff in warranty is being sued as personally liable. The warranty is termed formal if the plaintiff in warranty is being sued as the holder of a thing.
A third person called in simple warranty cannot take up the defence of the plaintiff in warranty, but may merely contest the application brought against the latter, if the person sees fit.
A third person called in formal warranty may take up the defence of the plaintiff in warranty and the latter may ask to be relieved from defending. In order to preserve their respective rights, the plaintiff in warranty, although relieved from defending, may remain in the proceeding and the principal plaintiff may require that the plaintiff in warranty remain in the proceeding. A judgment rendered against the formal warrantor is enforceable against the plaintiff in warranty after it is notified to the latter.