necessary family business is there for the sake of non witnesses and not for rank and file. The clause exists so that the society can say that shunning is a personal choice and at the same time print articles that state Df'd people are the walking dead and faithful christians will break all contact them. There is deliberately no application given because it does not apply to witnesses and specifics would reveal the cruelty of this arrangement to the wider world.
It is typical double speak and a phrase I have learnt to hate.