I had not seen any restriction on trailer wheels, but do know that trailer tires are typically marked as "trailer use only".
Given that the trailer wheel construction is probably identical to how car and truck wheels are made, it doesn't make much sense from and engineering standpoint that there would be a restriction to trailer use only.
This DOT standard says it applies to wheels for "multipurpose passenger vehicles, trucks, buses, trailers, and motor-cycles", so it appears that there isn't a separate standard for trailer wheels.
