§1. Unless the text of the sentence leaves it to the judgment of the executor, the executor must execute the sentence according to the obvious sense of the words.
§2. The executor is permitted to deal with exceptions concerning the manner and force of the execution but not concerning the merit of the case. If it is discovered from another source that the sentence is null or manifestly unjust according to the norm of cann. 1620, 1622, and 1645, the executor is to refrain from executing it and, after having informed the parties, is to refer the matter to the tribunal which rendered the sentence.
Source: Code of Canon Law (Vatican.va)