Hawks are considered an endangered species and if caught illegally killing a Hawk you can face up to 6 months in prison plus a $15,000.00 fine if convicted in court.
You can however kill a Hawk that is killing your chickens without obtaining a permit and if you live way out in the woods it's very unlikely that anyone is gonna know that you killed an endangered Hawk.
But if you're having trouble with Hawks Killing your chickens it would be in your best interest to get a permit so that it will be easy to get away with the killing of the hawk and you won't have to go through a legal process in proving you had to kill the hawk.
The permit for killing the hawk is much cheaper than the fine or prison time you could face if someone does turn you in for it.