You can not get a straight answer for that question. Heck even the DOT officers do not know the answer. I use to have a chart that outlined who needs a CDL but lost it in a hard drive crash.
Read the federal rules and make up your own mind.
The Federal standard requires States to issue a CDL to drivers according to the following license classifications:
To me this reads states have to follow the federal law and can not change them in any way.
Class A -- Any combination of vehicles with a GCWR of 26,001 or more pounds provided the GVWR of the vehicle(s) being towed is in excess of 10,000 pounds.
To me this says GCWR must be over 26,001 lbs AND the trailer GVWR must be over 10,000 lbs.
In other words a 25,000 lb truck with a 5000 lb trailer would not need a CDL because the trailer is not over 10,000 lbs.
A 14,000 lb truck with a 11,000 lb trailer would not need a CDL because the GCWR is not 26,001.
Class B -- Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing a vehicle not in excess of 10,000 pounds GVWR.
To me this was says the truck must have a GVWR of 26,001 or more.
Class C deals with haz mat and passengers so it is N/A for this question
Someone else brought up air brakes so lets answer that also.
There is no such thing as a Air Brake Endorsement. If you do not take the air brake test or fail the skill test you will be given a Air Brake Restriction. This restriction has no effect on what size truck you drive. It just can not have air brakes. I have seen many trucks (say a 2 ton) that can easily pull a trailer over 10,000 lbs and would have a GCWR over 26,001 lbs that did not have air brakes. Most have vacuum over hydraulic brakes on the truck and electric brakes on the trailer. This combo would require a Class A but could have the air brake restriction.
If a driver either fails the air brake component of the general knowledge test or performs the skills test in a vehicle not equipped with air brakes, the driver is issued an air brake restriction, restricting the driver from operating a CMV equipped with air brakes.