I posted before with clips from the Federal DOT site and PA State site, but here's another article to explain a little more about it on Truckinginfo.com. The combination wording can get a little tricky, but again it does state that IF the trailer is over 10,000# GVWR then you have to look at CDLs:
"CDL requirements become more confusing when the vehicle is towing a trailer.
There are three key aspects to consider when assessing CDL operator requirements for commercial work trucks involved in towing a trailer: truck GVWR, trailer GVWR, and GCWR of the truck-trailer combination. Trailer GVWR is most critical to determining when a CDL is required. When a trailer has a GVWR of 10,001 pounds or more and the combined GCWR of the truck and trailer is 26,001 pounds or more, a CDL is required by the operator. For example, if a trailer has a GVWR of 11,500 pounds and is towed by a truck with a GVWR of 15,000 pounds, resulting in a GCWR of 26,500 pounds, then the operator must have a CDL.
In contrast, when the trailer in the truck-trailer combination has a GVWR of 10,000 pounds or less, the CDL requirements allow for a greater GCWR for both the truck and trailer without requiring a CDL license. For example, a truck with a GVWR of 26,000 pounds or less can tow a trailer with a GVWR of 10,000 pounds or less and not require the operator to have a CDL under federal requirements. However, CDL requirements mandate that the truck and trailer GVW not exceed 26,000 pounds and 10,000 pounds, respectively. In short, the truck and trailer cannot be overloaded."
The article in full: www.truckinginfo.com/channel/equipment/article/story/2018/01/the-role-of-gvwr-and-gcwr-in-specifying-work-trucks.aspx