One of my duties at work is teaching/testing CDL drivers and I work with the Motor Carrier Enforcement officers next door quite often and the inaccuracies about CDL requirements is a pet peeve for us... The examples given are for NC (since that is where I am, as Chuck says above, check your locality for YOUR specifics, and keep a copy of the Statute with you in case somebody questions you about things).
Federal law is based on use of the vehicle as well as by weight (and by cargo type in the case of hazardous materials) as long as the driver is not compensated in any fashion; he will not need a CDL regardless of weight. The CDL is for Commercial (compensated) hauling.
So, if he is not hauling commercially:
He will need a non-commercial operator's permit if he:
Operates any single vehicle with a GVWR of 26,001lbs or more, and any such vehicle towing a vehicle (trailer) with a GVWR not in excess of 10,000lbs.
(The above in NC is a Class B)
Alternatively:
He will need a non-commercial operator's permit if he:
Operates any single vehicle with a GVWR of 26,001lbs or more, and any such vehicle towing a vehicle (trailer) with a GVWR in excess of 10,001lbs.
(The above in NC is a Class A)
The weight descriptions and classes are standardized from the CFR (Federal Regulations) with the NC class name given here as an example; other states may use different class names.
Since the testing requirements for CDL versus non-CDL operator's permits for any given class/endorsement combination are the same, it usually is just as convenient to go ahead and get the CDL and avoid possible issues in the future if somebody chips in for fuel, or pays your hotel room, etc., and a LEO decides to make an issue of it. You do have to get a medical waiver, but there are three different Federal exemptions for the medical card. Most of us can likely honestly meet one of the exception requirements.
That said, your locality is allowed to have more stringent requirements than that set forth in the Federal Codes. I'm not sure about California law, for instance, but I think that they have tinkered with the CDL requirements for their residents.
A CDL is a Commercial Operator's Permit and is issued for a given class of vehicle and has endorsements (such as air brake, tank, hazmat). It will state CDL Class X with the X being one of the classes such as I listed above.
A non-CDL Operator Operator's Permit is issued for the same given classes of vehicles and can have the same endorsements, but it will NOT have CDL listed on the license. It will just state that it is a Class B with Tank for instance.
Your "standard" non-commercial operator's permit does not list a class or endorsement for many states although quite a few have started listing the class/restriction.
An example (using NC again):
Class C: Operates any single vehicle with a GVWR of 26,000lbs or less, and any such vehicle towing a vehicle (trailer) with a GVWR not in excess of 10,000lbs.
North Carolina puts A, B, or C on the front of the permit with the class and the definition on the back. Endorsements (such as airbrake, tank, hazmat, etc.) are listed on the front by code with definitions listed on the back under the class definition.
If you get a CDL in NC, the permit gets a big "Commercial Driver License" right smack dab in the top center right between the "State of North Carolina" banner at the top and block of text that contains you name and address. If you don't have a CDL, the area where the CDL banner goes is blank.
One further bit that some folks overlook: You can get a CDL class C, hazmat. As an example: drive a van with a load of high explosives that are required to be placarded (application of those diamond tags on the front, back, and both sides warning everyone that you have hazmat, and listing by color, design, and number code what it is in order to inform emergency responders, bridge/tunnel inspectors, etc. of your load)
Hope this helps, and doesn’t confuse the issue too much…