I don't think there's any rules or laws. When it comes to Humans, normally if they're found they're pretty much devoured at a first come first serve basis. That was a reason why those who know Iruma's human worry for his safety of discovery. However, with Henri running the Demon Border Patrol, and thus having the higher chances of finding humans, he operated on finding, sheltering, and safely returning Humans to the Human world. There was no official law, simply the actions of an organization under one of the thirteen crowns control.
However, with Narnia's proposed act, humans, regardless of their situation or standing, can be forcibly removed from the Demon World with little care for their safety. Also, this could allow ample investigations on demons suspecting to be related to humans or offering them shelter, meaning that those demons could also be potentially punished for doing so. Of course, this is under the assumption that this act passes.