Every state in the Union has it's own use of force laws statutes. Counties, cities have local ordinances as well. If you intend to use a firearm for self defense via concealed carry or harth and home, it is your responsibility to know what those laws are. If you are unsure or find the laws ambiguous, find a credible criminal Defence attorney to sit down and explain it to you. If you can, look up case law. Remember, every use of force act will have two trials. Criminal and Civil. Don't rely on "my buddy's a cop". Law enforcement officers have different criteria involving use of force that are clearly laid out in statute. Besides, most law enforcement officers are not attorneys. No disrespect intended but I was a use of force instructor for my department so I speak from experience. Moss Ayoob is well respected and recognized as an expert in this field. He is the real deal. But even he would say he doesn't know everything. That's what makes him who he is. Paul Harrel has some very worth while thoughts on this matter as well.