Yes - you can wire them so that they are "legal" as reversing lights.
Simply power them through a relay, triggered by your existing reversing lights. You can even have a separate power feed to the lights so that you can switch them on for camping etc - but this switch MUST NOT be able to be operated from the driver's seat. I've got an LED light I've been meaning to mount off my rear wheel carrier for a while (will eventually get around to it

). This will have dual feed circuits - one via a relay triggered by the existing reversing lights, and one from a switch mounted inside the tailgate.
The circuit triggered by the existing reversing lights will also have a switch in the front so that I can turn the LED light OFF and NOT have it activated with the original reversing lights if I don't want it to come on. This is legal - provided that I cannot turn the LED light ON independently of the original reversing lights.
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