In VIRGINIA the trailer inspection stickers are placed on the driver's side trailer tongue as shown below.
Basically any trailer that has installed trailer brakes require a safety inspection here in Virginia. The safety inspection includes inspection of all trailer mounted lights where the rear lights all have to be DOT approved types. Tires and brake shoe/pads wear, and my last inspection I had to demonstrate that the electric brakes were actually working. When they had the trailer wheel jacked up for tire and brake shoe/pad inspection inspection I had to push in on my truck brake pedal while they tried to spin my trailer wheel. I had to tell them that my 2010 F150 Truck would not send power to my trailer brakes if I was under 10PMH speed using the brake pedal so I had to use the trailer brake slide level on the controller to activate the trailer brakes... I got my sticker so I guess I passed...
The first time I had my trailer inspected I had added white lights under the rear bumper and was told I would have to remove them or wire them up to operate when the truck was in reverse. I had my spotting lights wired to an ON/OFF switch inside the trailer. I was allowed to go home and remove them or make changes. I removed them from the rear and mounted on each side of the trailer in the rear frame area... Was better for me anyway as I can't see directly behind my trailer anyway... They said I could mount them high on the trailer in the rear if desired but that wasn't a good option for my POPUP.

My trailer inspection story...
Roy Ken
NOTE: I will remove my trailer inspection story if the OP so desires... Certainly don't want to upset anyone...