“Ob tacitam renuntiationem ab ipso iure admissam quaelibet officia vacant ipso facto et sine ulla declaratione, si clericus: A fide catholica publice defecerit.”
(1917 Code of Canon Law, Canon 188.4º)
“Any office becomes vacant upon the fact and without any declaration by tacit resignation recognized by the law itself if a cleric: Publicly defects from the Catholic faith.”
Did you read that, my friends? An office becomes vacant WITHOUT any declaration but by the law itself. This is because public defection from the Faith, such as heresy, itself severs the cleric from the Church. The cleric, no longer a member of the Church due to his public defection, loses his office, and this loss of office occurs without any declaration. So you can see that Canon 188.4º is the Church’s canonical formulation of the doctrine that public formal heresy itself severs one from the Church. This flies in the face of those who hold (heretically by the way) that one is separated from the Church for heresy only when the Church makes that judgement and not beforehand.