TECHNICALLY...the requirement is based on state laws. MOST states have a performance criteria for a vehicle towing another that says you must be able to demonstrate you can stop withing X feet from X MPHs. Some states do required brake systems based on weight of towed vehicle. You are bound to follow the laws of the state you are in, not the state of registry.
All that is fine and dandy but...
WHY NOT? I don't care if it only allows you to stop 10' shorter than without aux brakes...that could be the 10' that stops an insurance claim or worse.
Also...IMHO...a aux brake system is actually good for your car's front end alignment.
Don, Sandee & GSD Zeus. Gardian Wings earned are GSDs Gunny (7/11/15) & Thor (5/5/15)
2006 DSDP 4320, Spartan MM IFS, 2013 CR-V, Blue Ox Avail, SMI AF1, Samsung 197R Refer.