Promulgation in the canon law of the Catholic Church is the publication of a law by which it is made known publicly, and is required by canon law for the law to obtain legal effect. Universal laws are promulgated when they are published in Acta Apostolicae Sedis, and unless specified to the contrary, obtain legal force three months after promulgation. Particular laws are promulgated in various ways but by default take effect one month after promulgation.
Promulgation is the act by which the legislator manifests to those subject to his jurisdiction the decision that he has made and makes known to them his intention to bind them to the observance of his law.
Without having been promulgated, the canonical law in question has no legal effect, since promulgation is "an essential factor of legislation" and "an absolute condition for the effectiveness of a law".
For as law is a rational precept, no one can be bound to obey it if it have not been sufficiently made known to him. Ignorance takes away the voluntary ; and where there is nothing voluntary there can be no fault or punishment.
Promulgation is a "formal and fundamental element" of canon law. For the purposes of canonical jurisprudence, promulgation is equivalent to publication.
Once promulgation takes place, a canonical law acquires its last "essential condition" and takes immediate effect, subject to the vacatio legis imposed by universal law, or by the particular legislator issuing a law (see section below).
The nature of promulgation in its relation to the nature of canon law is a matter of discussion among canonical writers. Some canonists hold that promulgation as such "enters the very essence of the law", while Abbo & Hannan hold what they assert to be "the more probable opinion that promulgation is merely an extrinsic essential condition sine qua non."
For sufficient promulgation, the law must be published in such a way that it can come to the notice of the community, although it be not brought specially and singly before the notice of individuals.
A law issued by the Pope (or with his consent in the case of laws issued by an ecumenical council or congregation) is promulgated when it is published in Acta Apostolicae Sedis, and by default has the force of law three calendar months after promulgation.