Canon 194 provides that clerics who “publicly defected from the Catholic faith or from the communion of the Church” are removed from office by the law itself, but the loss of office has no juridical effect in the external forum until it “is established and declared by the proper authorities.”
Can. 194 §1. The following are removed from an ecclesiastical office by the law itself:
1º a person who has lost the clerical state;
2º a person who has publicly defected from the Catholic faith or from the communion of the Church;
3º a cleric who has attempted marriage even if only civilly.
§2. The removal mentioned in nn. 2 and 3 can be enforced only if it is established by the declaration of a competent authority.
The commentary on this canon found in "A New Commentary on the Code of Canon Law," by Beal, Coriden and Green, explains that cleric will retain the office and the acts will remain valid until the offences is established, declared, and communicated to him in writing.
"For all three situations competent authority must intervene. The clerical state is lost by declaration of invalidity of orders, imposition of the penalty of dismissal, or dispensation (c. 290); competent authority must act for each of these.
"In the other two situations of canon 194, competent authority declares the removal. These both involve delicts by the officeholds, and removal has the effect of a penalty. The canon is an exception to penal law, for removal from office is a permanent expiatory penalty (c. 1336 1, 2) which normally cannot be imposed or declared by decree (c. 1342. 2). Nevertheless, competent authority must determine the facts of the case and provide the officeholder with an opportunity to be heard (c. 50) before issuing the decree containing the reasons for removal and communicating this to the officeholder (c.51).
"Public defection from the Catholic faith is similar to but not precisely the same as apostasy (which is total repudiation of the Christian faith – c. 751); …
“In the case of defection [194, 2º] or clergy attempting marriage [194, 3º], the declaration by competent authority is similar to the declaration at the end of a term of office or completion of age. The fact on which the loss of office is based does not depend on the authority’s declaration, but its effectiveness does. The officeholder remains in office, and the actions which require the office are valid, until the declaration or removal is communicated to the officeholder in writing.”