Thank you everyone for your responses. The owners have been told multiple times that we will not feed the dog mice or dirt yet they still always bring the dirt. I'm not paid to blindly follow whatever instructions the owners give us, I'm paid to ensure the well-being of the dogs. We are transparent about not using the dirt or mice and that we give him water access 24/7, yet they still come in.
I figured that's what you guys did about the mice and dirt. Deefinitely sounds like these people are nutty and you probably won't be able to do anything unless the dog starts being in bad enough shape to involve the authorities. :/