Here in Washington state a CDL is required for any vehicle 26,000 lbs or over in less specifically licensed as an RV and if not obviously a motorhome it must be clearly marked for privet use not for hire.
This is a very gray area here.
The strange thing here is if you are driving a log truck with the trailer up on the back you are not required to stop but the same same empty truck with trailer on the ground or no trailer at all and you must stop. The signs here say all vehicles 10,000 and over must stop at scales as well but they get upset if you go through with a pickup truck with 12,000 GVW they clearly don't know what they want.
Yes CDLs are Federally regulated and the same state to state this was done for free commerce and to put and end to truckers holding licenses in multiple states.Weights measures and bridge laws will differ from state to state.Here in Washington with eight axles and proper axle spacing you can go as high as 105,500 lbs but California only allows 5 axles and 80,000 without special one time permits.
