The zoo near us in Kansas is off limits for firearms. I would hope if I saw this attack, maybe I would have been there early enough to warn the lady that we are just meat to the polar bear.
I guess since it is a hypothetical, you Michael be able to entice the polar bear with some fresh seal meat you happen to have near by or offer yourself up or someone you do not like very much.
In actuality, the scenario is, would you use your firearm when you are carrying illegally? This is a tough one since you will have had no justification as to why you broke the law. The concept of "competing harms" Mas Ayoob discusses would not seem to apply. If you expect to use force in places where your chosen weapon is not allowed, you should have a plan.
I have faced a simulation situation, but with vicious dogs in an area where there were playing children. I was legally armed and decided to drive the dogs off, though without the kids, I would probably have shot the dogs. The rules of engagement will vary according to the environment.