§1. By means of a private agreement made among themselves, the Christian faithful are free to establish associations to pursue the purposes mentioned in can. 298, §1, without prejudice to the prescript of can. 301, §1.
§2. Even if ecclesiastical authority praises or commends them, associations of this type are called private associations.
§3. No private association of the Christian faithful is recognized in the Church unless competent authority reviews its statutes.
Source: Code of Canon Law (Vatican.va)