#2 Definition of Commerce:
Commerce means (a) any trade, traffic or transportation within the jurisdiction of the United States between a place in a State and a place outside of such State, including a place outside of the United States and (b) trade, traffic, and transportation in the United States which affects any trade, traffic, and transportation described in paragraph (a) of this definition.
Conclusion: So where are we at now? By definition a Commercial Vehicle has to be used in COMMERCE to even be in the category of commercial vehicle.
Alright, now that we got that out of the way,
#3 Commercial Drivers License (CDL):
Commercial driver’* license (CDL) means a license issued by a State or other jurisdiction, in accordance with the standards contained in 49 CFR Part 383 , to an individual which authorizes the individual to operate a class of a commercial motor vehicle.
§383.23 Commercial driver’* license.
(a) General rule. (1) Effective April 1, 1992, no person shall operate a commercial motor vehicle unless such person has taken and passed written and driving tests which meet the Federal standards contained in Subparts F, G, and H of this part for the commercial motor vehicle that person operates or expects to operate.
(a)(2) Except as provided in paragraph (b) of this section, no person may legally operate a CMV unless such person possesses a CDL which meets the standards contained in subpart J of this part, issued by his/her State or jurisdiction of domicile.
Conclusion: Well, pretty straightforward. If you operate a large truck and you are involved in commerce, you need a CDL to drive said truck.
If I own a large truck that weighs 20k lbs and go pick up a Jeep (that I bought for myself to restore and enjoy) which weighs 5k lbs and pull it on my trailer that weighs 5k lbs, I do not need a CDL (by the federal regulations).
From the Federal Motor Carrier Safety Administration website FAQ'*:
Question 6: A driver operates a tractor of exactly 26,000 pounds GVWR, towing a trailer of exactly 10,000 pounds GVWR, for a GCWR of 36,000 pounds. HM and passengers are not involved. Is it a CMV and does the driver need a CDL?
Guidance: No to both questions. Although the vehicle has a GCWR of 36,000 pounds, it is not a CMV under any part of the definition of that term in §383.5, and a CDL is not federally required.
General applicability and definitions
§390.3 General applicability.
(a) The rules in subchapter B of this chapter are applicable to all employers, employees, and commercial motor vehicles, which transport property or passengers in interstate commerce.
(f)Exceptions. Unless otherwise specifically provided, the rules in this subchapter do not apply to—
(f)(1)All school bus operations as defined in §390.5;
(f)(2) Transportation performed by the Federal government, a State, or any political subdivision of a State, or an agency established under a compact between States that has been approved by the Congress of the United States;
(f)(3) The occasional transportation of personal property by individuals not for compensation nor in the furtherance of a commercial enterprise;
In case someone was going to throw out the "but if you can win prizes, awards, etc then you are involved in commerce" bs, here is another FMCSA website FAQ:
Question 21: Does the exemption in §390.3(f)(3) for the ‘‘occasional transportation of personal property by individuals not for compensation nor in the furtherance of a commercial enterprise’’ apply to persons who occasionally use CMVs to transport cars, boats, horses, etc., to races, tournaments, shows or similar events, even if prize money is offered at these events?
Guidance: The exemption would apply to this kind of transportation, provided: (1) The underlying activities are not undertaken for profit, i.e., (a) prize money is declared as ordinary income for tax purposes, and (b) the cost of the underlying activities is not deducted as a business expense for tax purposes; and, where relevant; (2) corporate sponsorship is not involved. Drivers must confer with their State of licensure to determine the licensing provisions to which they are subject.
Conclusion: It is not considered commerce and you are still exempt from needing a CDL as long as you don't deduct the cost of your trip/expenses as a business expense for tax purposes.