You have to pass a physical exam and the doctor has to sign off on it.
However much you can haul while still being within the limitations of that license. If the Gross Combined Weight Rating of the combination exceeds 26,000 lbs, then you're restricted to a trailer with a Gross Vehicle Weight Rating of 10,000 lbs. or less.
The EPA :Environmental Protection Agency .
It is to designate Class 1 - Explosives (dynamite, black powder).