Ok found the line in the Technical Regs about the Rear view mirror. See below!
CROSS-COUNTRY RALLY MOTORCYCLES
All vehicles must conform in all respects to the 1968 Vienna Convention, even
if the country in which the machine was manufactured is not a signatory to that
Convention, and be registered for road use.
Lighting and safety equipment
Lighting equipment for all categories must conform in every way to the International
Convention on road traffic, moreover:
The original headlights and rear lights may be modified or replaced. Extra lights
may be added.
Each motorcycle/quad must be equipped with at least:
A front light (min 55 watts or equivalent in lumen)
A generator with a required performance to support all requirements
An audible horn, minimum 90 dB/A, measured at one metre.
Minimum one rear view mirror.
A fixed water tank of 3 litres or a camel back with an equivalent quantity
All motorcycles/quads must carry the necessary survival equipment as requested
in the general regulations of the race.