i see tons of car and landscape and equipment trailers hauled by 1/2, 3/4, and 1 ton trucks all the time. many, but not all all hitches have a 500lb tongue / 5000lb trailer weight capacity unless used with a weight distributing hitch. i don't think i have ever seen correct hitch used on anything but the occasional camper. i can guarantee that some (and probably many) of them are exceeding the weight limit right there.
yes, the law may be black and white, but the application of the law for trailering seems to be handled with more of a gray attitude. probably 25%-50% of the trailers out there are some sort of moving violation. how many people know if their breakaway battery is charged? is the tongue weight or trailer weight distribution past the hitch rating, etc. generally when you see a trailer stopped and being checked, it LOOKS like a moving violation - missing fenders, bent frame, load unsecured, overloaded, swaying, mismatched tire sizes, etc.
as far as lawsuits go, in this country they have little to do with right and wrong, but everything to do with whether you can get money out of someone.