§1. General executory decrees, even if they are issued in directories or in documents of another name, do not derogate from laws, and their prescripts which are contrary to laws lack all force.
§2. Such decrees cease to have force by explicit or implicit revocation made by competent authority as well as by cessation of the law for whose execution they were given. They do not, however, cease when the authority of the one who established them expires unless the contrary is expressly provided.
Source: Code of Canon Law (Vatican.va)