Joint employer rules have never been that complicated. You want to know what makes them complicated, is that a Supreme Court judge can read regulations and say… oh well it says here that X is defined by Y, so we went back and found a case in 1930 that said that Y can be this, so that is the definition we are going to go by, and our ruling will set president for all future legal cases. Regulations don’t mean shit when the Supreme Court can interpret them however they like.