It was stupidity or ignorance on the part of the person who was bitten as any dog can become protective given the right circumstances.

However it's your brother-in-laws fault for allowing the incident to happen. The leash laws state that a dog owner must have their dog under control at all times.

He put the dog in a position where something like this could happen, knowing that the dog is protective and doesn't like men, it was his responsibilty to keep the dog under control and warn the neighbor to stay out of reach.

If the dogs had been seen by that vet; the vet is required to maintain a file on that pet with a copy of the rabies certificate attached. The rabies vaccination can also be confirmed by the local Rabies animal control agency.