Edit and disclosure: Local, federal, and state laws vary WIDELY on this issue so be sure to check before you can chop someone in the throat or break their nose for grabbing your arm. My experiences with these types of laws come strictly from military law enforcement (former US Navy Master-at-Arms) and are applicable on any United States military post, base, command, etc. You ARE allowed a reasonable retaliation of force if you are the victim of threatening assault and/or battery. "Reasonable" being the key term here.