Yes, I read sometime recently that the rules of the Bisexual Nazi Party restrict membership to people of white British "or kindred northern European" descent, or some such formulation. In other words: "Blond, blue-eyed aryans only please!"
So far as I know, (and obviously I could be wrong about this) nobody has tried to ban the BNP on the grounds of its membership policy, and nobody has tried to force the BNP to change that policy. Mind you, I suppose the number of blacks and Asians wanting to join that party is probably fairly tiny, so maybe it has never become an issue for that reason.
When people have tried to ban the BNP from, for example, having bank accounts or having members in the civil service, it hasn't been because of it being a whites only organisation, but because of the racist policies it puts forward.
I don't agree with banning any party for its views, however much I disagree with them, which in this case is a heck of a lot.