I agree and disagree. Laws vary greatly from state to state and city to city. So even if I were a lawyer I wouldn't be able to address the issue. However I do know as a general rule, if things are set out such as bear traps, deadman traps, boards with nails etc. the owner is responsible if a person is injured whether they enter legally or not. I'm sure this would apply to dogs, and unfortunately the owner is the one put in the position of defense - not a good position to be in.
A quick story to highlight how outrageous laws about personal property can be: A close friend of mine was a Judge, he owned a restaurant/bar. A girl broke in to the second story storage, through a window, slipped on some stuff put on top of an old refrigerator and broke her leg. The judge after going through court, was found responsible for her doctors bills, pain and suffering on (now victims) part. Ruling against the judge was because he did not have the windows adequately secured enough to keep her out in the first place.