[polak]

This might seem inhumane but how about a yearly dog evaluation? It would be mandatory and you'd have to pay into it so users pay for it and you'd test the dogs temperament off leash. Once you pass, you carry a registration card that shows your dog passed his yearly evaluation.

Dog doesn't pass, it gets put down.

In my opinion you would only fail if the dog showed serious signs of aggression. This would eliminate the possibility of having a guard dog, but I don't really care. You don't need a guard dog. Get an alarm. At least you can't lose momentary control of an alarm and have it maul someone.