Can. 7 A law is established when it is promulgated.
Can. 8
§1. Universal ecclesiastical laws are promulgated by publication in the official commentary, Acta Apostolicae Sedis, unless another manner of promulgation has been prescribed in particular cases. They take force only after three months have elapsed from the date of that issue of the Acta unless they bind immediately from the very nature of the matter, or the law itself has specifically and expressly established a shorter or longer suspensive period (vacatio).
§2. Particular laws are promulgated in the manner determined by the legislator and begin to oblige a month after the day of promulgation unless the law itself establishes another time period.
Can. 9 Laws regard the future, not the past, unless they expressly provide for the past.
Can. 10 Only those laws must be considered invalidating or disqualifying which expressly establish that an act is null or that a person is effected.
Can. 11 Merely ecclesiastical laws bind those who have been baptized in the Catholic Church or received into it, possess the efficient use of reason, and, unless the law expressly provides otherwise, have completed seven years of age.
Can. 12
§1. Universal laws bind everywhere all those for whom they were issued.
§2. All who are actually present in a certain territory, however, are exempted from universal laws which are not in force in that territory.
§3. Laws established for a particular territory bind those for whom they were issued as well as those who have a domicile or quasi-domicile there and who at the same time are actually residing there, without prejudice to the prescript of can. 13.
Can. 13
§1. Particular laws are not presumed to be personal but territorial unless it is otherwise evident.
§2. Travelers are not bound:
1. by the particular laws of their own territory as long as they are absent from it unless either the transgression of those laws causes harm in their own territory or the laws are personal;
2. by the laws of the territory in which they are present, with the exception of those laws which provide for public order, which determine the formalities of acts, or which regard immovable goods located in the territory.
§3. Transients are bound by both universal and particular laws which are in force in the place where they are present
Can. 14 Laws, even invalidating and disqualifying ones, do not oblige when there is a doubt about the law. When there is a doubt about a fact, however, ordinaries can dispense from laws provided that, if it concerns a reserved dispensation, the authority to whom it is reserved usually grants it.
Can. 15
§1. Ignorance or error about invalidating or disqualifying laws does not impede their effect unless it is expressly established otherwise.
§2. Ignorance or error about a law, a penalty, a fact concerning oneself, or a notorious fact concerning another is not presumed; it is presumed about a fact concerning another which is not notorious until the contrary is proven.
Can. 16
§1. The legislator authentically interprets laws as does the one to whom the same legislator has entrusted the power of authentically interpreting.
§2. An authentic interpretation put forth in the form of law has the same force as the law itself and must be promulgated. If it only declares the words of the law which are certain in themselves, it is retroactive; if it restricts or extends the law, or if it explains a doubtful law, it is not retroactive.
§3. An interpretation in the form of a judicial sentence or of an administrative act in a particular matter, however, does not have the force of law and only binds the persons for whom and affects the matters for which it was given.
Can. 17 Ecclesiastical laws must be understood in accord with the proper meaning of the words considered in their text and context. If the meaning remains doubtful and obscure, recourse must be made to parallel places, if there are such, to the purpose and circumstances of the law, and to the mind of the legislator.
Can. 18 Laws which establish a penalty, restrict the free exercise of rights, or contain an exception from the law are subject to strict interpretation.
Can. 19 If a custom or an express prescript of universal or particular law is lacking in a certain matter, a case, unless it is penal, must be resolved in light of laws issued in similar matters, general principles of law applied with canonical equity, the jurisprudence and practice of the Roman Curia, and the common and constant opinion of learned persons.
Can. 20 A later law abrogates, or derogates from, an earlier law if it states so expressly, is directly contrary to it, or completely reorders the entire matter of the earlier law. A universal law, however, in no way derogates from a particular or special law unless the law expressly provides otherwise.
Can. 21 In a case of doubt, the revocation of a pre-existing law is not presumed, but later laws must be related to the earlier ones and, insofar as possible, must be harmonized with them.
Can. 22 Civil laws to which the law of the Church yields are to be observed in canon law with the same effects, insofar as they are not contrary to divine law and unless canon law provides otherwise.