§1. An act placed out of force inflicted on a person from without, which the person was not able to resist in any way, is considered as never to have taken place.
§2. An act placed out of grave fear, unjustly inflicted, or out of malice is valid unless the law provides otherwise. It can be rescinded, however, through the sentence of a judge, either at the instance of the injured party or of the party’s successors in law, or ex officio.
Source: Code of Canon Law (Vatican.va)