This used to be the case, but now I am not sure. My dirtbikes are plated/ registered in colorado (where as long as it is plated, you don't need an ohv sticker offroad) but they starting handing out tickets in utah license plate or not, even if it was ohv stickered in another state if you were on the trails with out a Utah OHV sticker. Also, they arent as lenient as they used to be about non street legal rigs. They will give out tickets. Even for the lame-o utah mudflap and fender flare laws (which is ridiculous and illegal if it is legal in your own state). So now I don't know what to say. Usually there wont be anyone around to notice/ care except on the weeks surrounding Easter. Easy to buy a sticker though. The ranger office in Moab should be able to clear up any questions.