Used to happen all the time. I just popped outside and said "you realise if he bites you i'm not calling an ambulance right?". I generally do this with a cheeky grin.
If said person laughs, then you talk to them for a bit. If they walk off, then problem solved, oi, dog, get back inside, you ain't meant to be out.
If said person laughs, then you talk to them for a bit. If they walk off, then problem solved, oi, dog, get back inside, you ain't meant to be out.