"There is no excuse for believers continuing to associate with … and those who, knowing everything, still insist on doing so, should be shunned by their fellow-Bahá’ís. The same applies to people who have left the Cause and associate with …. The point is that if the believers know and meet with people who are acquainted with Covenant-breakers there is no harm in this, for such individuals are not Bahá’ís and have nothing to do with the issues concerned. But those who have left the Cause, knowing all about such matters, and deliberately associate with Covenant-breakers, are well aware of what they do, and we must not associate with them at all. It is for the Local Assembly, guided by the N.S.A., to enforce such decisions and protect the Cause in its area of jurisdiction."
(From a letter written on behalf of the Guardian to an individual believer, January 23, 1945)
http://bahaism.blogspot.com/