Usacarry.com had a thread much like this. The legalities can be more state specific, BUT the question would probably rest on you feeling threatened. Your dog was probably acting in your defense, so as you described the situation. I would have felt threatened if I were you.
At the very least you probably have a civil case for your dog's vet bills.
A dog (especially a known breed) used for protection has the ability to cause you SERIOUS harm if it attacks. Your state probably has specific laws listed.