The real experts, those who work around grizzlies every day, generally have someone with them who has a 12-gauge shotgun loaded with "flash-bang" shells. These a basically loud firecrackers and are used to scare a charging critter, not to harm it, and they work. Between the sound of the shot and the "BANG!" of the firecracker the bear or other critter heads off in another direction. don't even think of this unless you know what you're doing.

Park Rangers are scared shitless because people are now allowed to carry firearms in the National Parks, except into buildings. BUT it is totally forbidden to discharge them ("You can carry 'em, Congress said so, but you can't shoot 'em!"). The rangers are afraid of two things: someone's gonna think a naturally curious bear is attacking and it will be shot with a .22 by a panicky tourist and then the Rangers WILL have to "put it down" OR some drunken lout with shoot someone over a campsite dispute. So are the locals, who will have to deal with the results of such stupidity just as the Rangers do...you don't think there's a hospital in Yellowstone, do you?