Arkansas already, sort of, has this as law.
In the Arkansas statute, there is a "duty to retreat" statement, but it is also qualified by the phrase "with absolute safety."
In Arkansas, in a public place, you have a duty to retreat from a threat, but only if you can do so with "absolute safety," whatever the heck "absolute safety" means.
Basically, there's no such thing as an "absolutely safe" retreat from a person who is trying to harm or kill you. At least any competent attorney could argue it that way.
Unless, let's say, you are in an amored personnel carrier, the attacker is armed with a rubber hose, and you can merely back up at 20 mph.
But even though Arkansas has a "duty to retreat" law, we've also got the "with absolute safety" qualifier in the law, which really murks things up.
hillbilly