The court’s basis for affirming this protection was existing precedent that negative discrimination is still illegal if based on a characteristic that the discriminating party perceived the discriminated party to have, whether or not that perception is correct. (Concrete [invented] example: if someone were discriminated against on the basis of a Jewish-sounding or Muslim-sounding name, but were not actually Jewish or Muslim, they could still claim religious and racial discrimination.)
For this protection, a Gender Recognition Certificate is irrelevant, since it is based on perceptions, not facts.
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