MCA 61-1-101 (82) (a) & (b):
"(82) (a) "Trailer" means a vehicle, with or without motive power, other than a pole trailer, designed for carrying property and for being drawn by a motor vehicle and constructed so that no part of its weight rests on the towing vehicle.
(b) The term does not include a mobile home or a manufactured home, as defined in 15-1-101."
Note that a "trailer" is "...designed for carrying PROPERTY and for being DRAWN BY A MOTOR VEHICLE...".
Most motor vehicles are designed for carrying PEOPLE, and must be MODIFIED to be drawn by a motor vehicle.
Yes, I am well aware that MCA only applies to vehicles operated in Montana!