Apparently the rules have changed a little starting Sept. 2nd.

Yellowstone rules

They allow you to carry both sidearm and rifle in Yellowstone. But you can't take them everywhere apparently.

Something else you might want to check out This . I found this last year and after going through most of it was pretty impressed on the amassed information. Don't let the title fool you, the document goes through current knowledge of bear behavior, how to respond, and because it is a management of resource guide it shows target areas for the side and FRONT of bears when hunting a problem bear.