The only law a work is Darwins Law and the fear of some idiot standing, getting hurt and suing. Its not like this hasn't happened before and, generally, lap bars and/or announcement cover it. In the instance of SE, its a ride that suddenly spins 180 and goes backwards, so Im sure there are people who get freaked out about it. On a ride like Everest, Im sure the lapbar and roller coaster aspect are enough for a common person to figure it out.
Remember...most precautions are there because some idiot, at some point, thought "I should try to swim in jungle cruise".