If he has them split up, then he would need a couple of the kp locks, otherwise nothing stopping anyone hooking up to them I guess.
Here in the West, 3" and 3.5" diameter king pins are common and you need a turntable with the correct size jaws to hook up, where as most on the eastern seaboard are 2"diameter. That would deter most with a 2" turntable hooking them up