Nick Griffin has stated that the party relies on ss. 25 - 26 of the 1976 Race Relations Act for the ban; this states
An association [ ... is exempt ...] if the main object of the association is to enable the benefits of membership (whatever they may be) to be enjoyed by persons of a particular racial group defined otherwise than by reference to colour; and in determining whether that is the main object of an association regard shall be had to the essential character of the association and to all relevant circumstances including, in particular, the extent to which the affairs of the association are so conducted that the persons primarily enjoying the benefits of membership are of the racial group in question.It seems to me there are two fascinating legal points that will form the crux of any legal challenge. Firstly, whether a political party is an association for the benefits of its members. Secondly, whether the 'indiginous British' are a distinct racial group.
It's the second that will prove most fascinating. The BNP says "We use the term indigenous to describe the people whose ancestors were the earliest settlers here after the last great Ice Age and which have been complemented by the historic migrations from mainland Europe. The migrations of the Celts, Anglo-Saxons, Danes, Norse and closely related kindred peoples have been, over the past few thousands years, instrumental in defining the character of our family of nations."
And here I must re-read Bryan Sykes' excellent 'Blood of the Isles'. From what I recall, the Romans, Angles, Saxons, Jutes, Danes and Normans barely left a genetic footprint in our DNA. We are overwhelmingly Celtic, even in Kent and Surrey. But Celtic-ness is not unique to the inhabitants of these isles - both France and Spain have Celtic populations.
Anyway, I hope it comes to court - I'd love to hear the legal arguments on both sides.