I have found that in many cases people have misinterpreted the laws, or have been given bad information by someone, for example towing Trains (two trailers) is permissible in Ontario in very few cases, , usually restricted to commercial registered vehicles, and drivers, however we see it all the time with truck-camper-boat combos. it's illegal, but usually MTO ignores it. I would bet if there was an accident, it would no longer be ignored in that case.
Trailer gross weights are another issue, you have to combine the
weight of the trailer, and the
weight of the load in determining brake requirements, but common misconceptions like if it has brakes they need to be hooked up, and if it's registered gross if 6000lb, then it has to have brakes in Ontario are only misconceptions.
You need to check your state laws, and anywhere you will be towing
Joe