As a retired LEO, I did a lot of research on this and believe me, it is the law. NV does recognize my ID drivers license for RV double towing and I checked with the NV SP in Reno, just to be sure. Now, go to a state that does NOT allow RV doubles, like most of the east coast and my license means nothing, as it is against the law for ANYONE to tow RV doubles.
EX:
CA DRIVER LICENSING for DOUBLE TRAILERS - CALIFORNIA RESIDENTS
12804.9. (b) ..., any applicant for a driver's license shall be required to submit to an examination appropriate to the type of motor vehicle or combination of vehicles the applicant desires a license to drive:
(1) Class A includes the following:
(A) Any combination of vehicles, if any vehicle being towed has a gross vehicle weight rating of more than 10,000 pounds.
(B) Any vehicle towing more than one vehicle.
(C) ...
15278. (a) A driver is required to obtain an endorsement issued by the department to operate any commercial motor vehicle that is any of the following: (1) A double trailer. (2) ...
To apply for a commercial driver license, see this DMV web site: http://www.dmv.ca.gov/commercial/commercial.htm.
DRIVER LICENSING for DOUBLE TRAILERS - NONRESIDENTS
12502. (a) The following persons may operate a motor vehicle in this state without obtaining a driver's license under this code: (1) A nonresident over the age of 18 years having in his or her immediate possession a valid driver's license issued by a foreign jurisdiction of which he or she is a resident, ....
(b) Any person entitled to the exemption contained in subdivision (a), while operating, within this state, a commercial vehicle, as defined in subdivision (b) of Section 15210, shall have in his or her possession a current medical
In summary, nonresidents may tow two trailers with a non-commercial license IF their base state allows it. However, they would still need a valid medical certificate per 12502 CVC.