I think it is everyones responsibility to tell someone they are breaking the law. Although I also think this could be quite dangerous now days too.
I seem to remember a story a couple of years back about a guy who took a gun away from someone at reiter and proceded to thump him. I'd opt to just use the old cell phone and let the guys who get paid for it take care of the problem.
This brings up another subject too. The WDF is always complaining about the lack of funds, but why aren't they out writting tickets to these people and generating revenue. I'm sure they know that the fall salmon season brings out the crackers.
Just my .02$