If a brother in Christ chooses to enter public life and declares openly that he is a brother, then he is bound to publicly behave as one of us.

If that brother publicly turns from the Truth then he is bound to recant his membership in as public a fashion as he has made know his former membership. (1 Eye = 1 Eye)

Having claimed himself a Catholic he is assumed to know Her teachings. In this matter, we are told to admonish privately and then PUBLICLY. (Matthew 8:15-17)

…and if he refuses to listen even to the church, treat him as you would a pagan or a tax collector.