Excommunication

[CatholicCid]

Can the Church excommunicate a person? Or can they just acknowledge that a person has excommunicated themselves?

If the Church excommunicates a person, does that mean that the Church has declared that the person is no longer in Communion with Her, or it She just recognizing that the sins and disobedience committed by that person has cut off their Communion.

[cappie]

Short answer is both.

Can. 1314 Generally, a penalty is ferendae sententiae, so that it does not bind the guilty party until after it has been imposed; if the law or precept expressly establishes it, however, a penalty is latae sententiae, so that it is incurred ipso facto when the delict is committed.

If the penalty is imposed latae sententiae then there is no need to have it declared although it can be.

Canon Law warns

Can. 1318 A legislator is not to threaten latae sententiae penalties except possibly for certain singularly malicious delicts which either can result in graver scandal or cannot be punished effectively by ferendae sententiae penalties; he is not, however, to establish censures, especially excommunication, except with the greatest moderation and only for graver delicts.