I've never heard of or seen a law that actually prohibits it. And I don't know why such a law would be needed. Tree stands work well for deer, largely because they don't deal with predators killing them from above so they don't look up a lot. Turkeys, however, deal with arial predators from the day they hatch. They pay attention to what's above them. There have been several times I've had turkeys pass under me while deer hunting. Even while bow hunting without orange, sitting stone still, they'll pick you off. It's just not much of an advantage. An enclosed box stand, sure, but that's no different that a pop-up tent. I don't like pop-up tents, but I can't rationalize a legal distinction between hunting from an enclosed structure on the ground vs. an enclosed structure 10 ft off the ground.