I found this statement on the Yellowstone National Park "Laws and Policies" page https://www.nps.gov/yell/learn/manageme ... licies.htm
I suspect the above would be used to set up "bear spray and other safety precautions" as alternatives to the discharge of a firearm, rendering the use of a firearm unnecessary for self defense. I'm not a lawyer either but it strikes me a test case would be needed to sort this out.Firearms should not be considered a wildlife protection strategy. Bear spray and other safety precautions are the proven methods for preventing bear and other wildlife interactions.
By the way, our tour guide also mentioned an encounter with a bear where the bear killed someone and, in the process, chewed a hole in his can of bear spray. Not sure if that was hyperbole but it makes one wonder.