bans cannot be made on classification of a specific product.
e.g. to make this into a law - projection of light onto the road from a motor vehicle needs to be defined, its not defined as "fallana HID is allowed and fallana halogen bulb is not" - its defined in length, pattern, height, brightness, colour temperature etc.
now you may go out and install sodium vapor bulbs in your car or even light up a diya and place it inside your headlamp, if it does not meet the legal requirements - its not allowed. end of story.
to test, take a car with HID installed in halogen reflector housing and try to aim it on a testing wall, you will see the light cut pattern is not even there - forget about aiming. - This automatically qualifies is as not road legal no matter if you have retrofitted jenyan japani toita ki HID masheen aur bulapp, relay ke saath and it can be anywhere in the rainbow spectrum.
The problem is the shoda type of idiots whose first job of the day is to ask abba for his card/cash and then proceed to dekorashan shaap and ask him to place HIDs in
headlamps
fog lamps
brake lamps
gauge cluster
interior
a few extra just in case - because F&F cars had them everywhere including the engine room.