I didn't find any thing about it on the internet! Thanks though!
And Jump4Heaven: I didn't know that about trail riding. I only went on a trail ride at a state park here.
I don't make people sign waivers but I don't let them ride without me leading them on a line no matter how experienced and if they are under age I make their parents watch. I should print out some waivers just to be on the safe side.