Are you referring to one of these:
Click here.Every state has their own rules, and how much they enforce those rules too.
I do know, in Indiana, the use of the "swivel wheel" trailer is legal, even behind a 5er or a TT. But, because it has a wheel, and the wheel touches the ground, it has to be registered and licensed as a trailer, have it's own license plate, and be equipped with turn signals and brake lights. Because it's under 3000 pounds it does not need a brake.
The carriers that attach to the rear, via a receiver hitch, or even mounted via the frame, does not need any kind of license because it has no wheel that touches the ground.
Like I said, every state has their own peculiar laws. How much one state honors the laws of another state, is really a state-to-state issue. Best to check with DMV or law enforcement of the visiting state.