Hello Paikea, I don't think there this a law for these tow bar connection, But for example you don't want go down the highway and say the trailer comes of the tow ball if your got a shit/ cheap d shackle with the weight and motion the will break / snap / stretch , and disconnect then if at speed your trailer will go anywhere. You want it to stay connected. That's why everything has to be rated , proply, You see now with these new 4wd;s that the tow bar has d shackles on both sides at the bottom there painted yellow and there the proper rated d shackles. If you are to connect trailer to car then you need these to be again d shackle that are rated. You cant put just any cheap shackle on your trailer cause under weight they wont hold. And I don't think INSURANCE will tell you this until its to late , THEN SORRY THEY SAY YOU HAVE NOT THE RIGHT RATED CONNECTIONS. I myself have a big boat and one day, I broke down up the coast , the towie put my car on the tilt tray and boat he towed home , on the way home this truckie pulled up next to us and talking on the CB he said is that you towing the boat , Yes it is . What happened is cause of bounce in the road the d shackle that held the boat down on trailer on the front could not handle the load so the boat was bouncing around on the trailer the only thing holding the boat was the strap on the back, SHIT I WAS LUCKY. So that's my point, there are lots of people out there who don't connect to there trailers proply. It is a touchy subject which I don't think many people take much care about until its to late. And I don't take offence about at your comments SAFTY FIRST that's why where here for taking advise and listen to others and there views. But I think everyone should take NOTICE and check there trailers.