flocksalot, you may want to verify this and ask a game warden or someone. It sounds to me like you can take care of problem dogs.
This is from your state's website: http://docs.legis.wisconsin.gov/statutes/statutes/174.pdf
174.01(b) A person may intentionally kill a dog if a domestic animal
that is owned or in the custody of the person is threatened with
serious bodily harm by the dog and the dog is on property owned
or controlled by the person and:
1. Other restraining actions were tried and failed; or
2. Immediate action is necessary.
This is from your state's website: http://docs.legis.wisconsin.gov/statutes/statutes/174.pdf
174.01(b) A person may intentionally kill a dog if a domestic animal
that is owned or in the custody of the person is threatened with
serious bodily harm by the dog and the dog is on property owned
or controlled by the person and:
1. Other restraining actions were tried and failed; or
2. Immediate action is necessary.