§1. Unless particular law establishes otherwise, the bishop of the diocese in which the sentence was rendered in the first grade must execute the sentence personally or through another.
§2. If he refuses or neglects to do this, the execution of the sentence, either at the request of an interested party or even ex officio, pertains to the authority to whom the appellate tribunal is subject according to the norm of can. 1439, §3.
§3. Among religious the execution of the sentence pertains to the superior who rendered the sentence to be executed or the superior who delegated the judge.
Source: Code of Canon Law (Vatican.va)