Hi. The rules directly state no dog has to scratch into a dead dog.
The whole point of the Cajun rules (scratching), as opposed to just leaving them down until 1 is dead, is to AVOID death.
The referee can't "declare a winner" if two dogs are still fighting, but if one dog is gone and just being dragged around the pit dead, he can declare a winner like that.
In any case, anyone leaving his dog down to die isn't exactly the height of "class" and "sportsmanship."
Jack