It doesn't, and the question asked doesn't imply that.
The BNP state (unfortunately I can't get on the site properly at the moment) that they will use legal, finanicial and social programs to encourage people to return to their country of ethnic origin (including people born in the UK). Or in other words, they will make their lives miserable and then offer them some money go somewhere else.
It's not compulsory, but if it was employment, it would be constructive dismissal.
In this case, they possibly do. Refusal to be honest about party believes and the press then representing you as your party believes would seem to redress the balance a little. Griffin refuses to be honest about what his party (constitutionally) stand for in interviews, but the constitution is publicly available, as are their polices and stances on issues such as miscegenation. Reporting Griffin's words in a way compliant with the beliefs of his party are a good retort to his refusal to be honest.