Yellostone is a National Park, therefore ALL crimes, no matter how petty or serious, would be charged as a federal crime. They would be prosecuted under Federal Law instead of state laws. Just like many of the indian reservations are punitively charged under federal statutes not state law.
There’s a small portion of the park where supposedly a legal loophole exists.
But, it’s just a theory that’s talked about. No one has really tested the theory.
However, if someone believed that theory, he might plan a crime there, thinking he can’t be prosecuted.