It is tragic for everyone involved. I do not see how the owners were intent on being abusive to the dog. They probably did not have a fence for him and thought that would be adequate. It may have been with a different dog. Large, young dogs can get themselves into all sorts of trouble.
I would guess the owners were at work. It is tragic, but probably they feel terrible enough already. I doubt they knew the particulars of the current time restraint law.
Everyone is a little too quick to judge. Maybe the owners are monsters, but I doubt it. They probably loved that dog.
Before you flame, i’m not sticking around to fight about it. Condemn the owners to death if you want.
"Look, honey! Rover chewed his leg off!"
"Splendid. Let's wait and see if it gets infected before we ditch him."