That depends on which state you live in. AFAIK (essentially picked up off various news groups and web boards), in some states you'd be entitled to shoot to protect property, but in others you wouldn't be allowed to unless you were in fear of your life and hade no way to escape.

From what I've heard, the dos and don'ts are well covered in the gun classes that many states require for you to be able to get a CCW permit.

/Michael