A few years ago a friend of mine was pulled over on Rt2 in MA with his work truck. He was driving an F350 dually (company truck with lettering) with tool body. He was towing a 14K lbs bumper pull trailer with a track skid steer. The officer made him go through the truck, show proof of a pre-trip, checked the function of the trailer brakes and emergency brakes, and checked his Class A CDL. The officer was targeting (vocally) small contractors and landscapers who thought they could get away without a CDL in a dually truck and trailer.
See in MA, you need to comply with the federal rule of the Single or combined GVWR of 26K but also, MA regulates trailers over 10K as requiring a CDL. Son in NH I can tow a 14K trailer with my pickup, but once I cross the state line, I'm in violation (no CDL).
He was operating a commercial vehicle for commercial purposes. If he was driving a dually with a normal bed towing the exact same load. The police officer would not have done this inspection. In MA you can tow a trailer over 10K with a combined GVW over 26K and you will be within the law. In MA they recognize the C in CDL stands for Commercial.