Here is what that list says about Montana:
Montana
All trailers and pole trailers with a Gross Vehicle Weight (GVW) of 3,000 lbs. or greater must be equipped with brakes acting on wheels. All trailers and pole trailers with a GVW of less than 3,000 lbs. must be equipped with brakes on all wheels if the total weight of the trailer or trailers does not exceed 40% of the GVW of the towing vehicle.
Every trailer and pole trailer equipped with air- or vacuum-actuated brakes and every trailer and pole trailer with a GVW in excess of 3,000 lbs. must be equipped with brakes acting on all wheels that are designed to be applied automatically and promptly, and remain applied for at least 15 minutes upon breakaway from the towing vehicle.
A towing vehicle and all trailers being towed must have 1 control device that can be used to operate all service brakes.
Here is the actual Montana law:
61-9-304. Brakes required on all wheels -- exceptions. Every vehicle must be equipped with brakes acting on all wheels except:
(1) trailers, semitrailers, pole trailers of a gross weight not exceeding 3,000 pounds, provided that:
(a) the total weight on and including the wheels of the trailer or trailers may not exceed 40% of the gross weight of the towing vehicle when connected to the trailer or trailers; and
(b) the combination of vehicles consisting of the towing vehicle and its total towed load is capable of complying with the performance requirements of 61-9-312;
(2) any vehicle being towed in driveaway or towaway operations, provided the combination of vehicles is capable of complying with the performance requirements of 61-9-312;
(3) trucks and truck tractors having three or more axles need not have brakes on the front wheels, if the vehicle was manufactured before July 25, 1980. However, the trucks and truck tractors must be capable of complying with the performance requirements of 61-9-312.
(4) special mobile equipment;
(5) the wheel of a sidecar attached to a motorcycle or to a motor-driven cycle, or the front wheel of a motor-driven cycle need not be equipped with brakes. However, a quadricycle, motorcycle, or motor-driven cycle must be capable of complying with the performance requirements of 61-9-312.
Can you see what the "list of laws" left out?
Note that if the combination of vehicles can comply with the provisions of MCA 61-9-312, trailer brakes are NOT required!
Now, exactly what IS a "trailer"? For the answer, we need only look at MCA61-1-101(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 upon the towing vehicle.
(b) The term does not include a mobile home or a manufactured home, as defined in 15-1-101.
Note that the definition is very specific; a trailer is designed for carrying PROPERTY, and for being DRAWN BY A MOTOR VEHICLE.
An automobile is designed primarily for carrying PEOPLE, and is NOT designed to be towed, it must be modified for the purpose.
While the quoted list is fairly accurate, I can only say again, do NOT rely on ANY list of towing laws that you find on the internet. That list will not make a good witness if it comes to a court case!