willald, strangely enough, NC is one state that actually HAS a requirement for aux. braking!
North Carolina Statute 20-124 (f) "Every semitrailer, or trailer, or separate vehicle, attached by a drawbar or coupling to a towing vehicle, and having a gross weight of two tons, and all house trailers of 1,000 pounds gross weight or more, shall be equipped with brakes controlled or operated by the driver of the towing vehicle, which shall conform to the specifications set forth in subsection (e) of this section and shall be of a type approved by the Commissioner."
The gross weight limit is 4000 lbs., and the brakes must be controlled or operated by the driver!