I live near a very popular NP and the rangers there won't hesitate to taser if you give them trouble. I never have had any issues with a park ranger, most of em are pretty cool if you are responsible and respectful.
For a number of years some idiots were hosting a 'fest right near one of the park gates. Large crowds, live music and the smell of hemp filled the air. One gal decided to run thru the park gates and the rangers wasted no time in tasering her. Also hear of rude intoxicated subjects getting the taser treatment all the time in the park.
