I can't find the exact wording, but when your trailer by itself weighs more than 10,000 pounds, you need a CDL to pull it if it's not farm or recreational.
I have the VT book. If I understand, other States each have their rules, but they align with each other when they can.
Vermont states the nameplate GVW of the trailer triggers the absolute CDL requirement at 10,000 LBS. This is not scale weight, this is manufacturer rated weight.
Several paragraphs later they list an exemption for truck & trailer nameplate total under 26,000.
In VT, you can drive a 14000 LB rated trailer towed by a 12,000 LB GVWR truck without a CDL. A 14,000 ratedtrailer towed by a12,001 LB rated truck needs a CDL class A license.
Truth is: many Troopers don't know this.
A young friend called me one day. He was working on Martha's Vineyard Massachusetts, his boss sent him to VT to bring a truck load of steel back. Island prices are crazy, they could buy steel in VT, with trucking & ferry fees it was cheaper up here.
The truck he drove was rated 25,000 GVWR. It was well under rated load. The driver was a licensed Vermont resident. Vermont Troopers red flagged the truck, quoted a vague law that doesn't exist. No fine, but they wouldn't let him finish his trip to Massachusetts. A Vermont CDL driver was needed to drive the vehicle to the State line.
It made no sense. There was no law cited he had violated. It wasn't worth the legal battle. I drove the truck to the Mass. State line, he finished his trip.