Many, many years ago when our son was attending college in Powell WY, my husband stopped in at the ranger's office to see if he was allowed to fly his small plane over the Park. He was told that he shouldn't fly over the populated areas because the tourists didn't like the noise...and by the way, he couldn't land in the Park. He asked if there was an airstrip and was told no. He told the ranger, "If that thing out in front of me stops spinning, I AM landing in the Park". Ranger was not amused.
I would imagine that if it were possible to do a chopper tour over the Park, there would already be concessionaires providing the service. People go to Yellowstone for things other than hearing noise.
This being said, there could very well be further regulations by this time.