For Illinois:
Vehicles Requiring a CDL
Any combination of vehicles with a Gross Combination Weight Rating (GCWR) of 26,001 pounds or more, providing the Gross Vehicle Weight Rating (GVWR) of the vehicle being towed is in excess of 10,000 pounds.
Any single vehicle with a GVWR of 26,001 pounds or more, or any such vehicle towing another not in excess of 10,000 pounds.
Any vehicle, regardless of size, designed to transport 16 or more persons, including the driver.
Any vehicle, regardless of size, required by federal regulations to be placarded while transporting hazardous materials.
Reading this my take is that if the vehicle being towed is over 10,000# AND the total weight of all the vehicles (truck and trailer) is over 26,001# THEN you need non-commercial CDL. In Teamubr's case he is over the 10,000# on the trailer, but is under the 26,001# total, so he would be exempt.
Bit tricky, had to read through it a few times.