19 There is a great variety of associations in the apostolate. Some set before themselves the broad apostolic purpose of the Church; others aim to evangelize and sanctify in a special way. Some purpose to infuse a Christian spirit into the temporal order; others bear witness to Christ in a special way through works of mercy and charity. Among these associations, those which promote and encourage closer unity between the concrete life of the members and their faith must be given primary consideration. Associations are not ends unto themselves; rather they should serve the mission of the Church to the world. Their apostolic dynamism depends on their conformity with the goals of the Church as well as on the Christian witness and evangelical spirit of every member and of the whole association. Now, in view of the progress of social institutions and the fast- moving pace of modern society, the global nature of the Church's mission requires that apostolic enterprises of Catholics should more and more develop organized forms in the international sphere. Catholic international organizations will more effectively achieve their purpose if the groups comprising them, as well as their members, are more closely united to these international organizations. Maintaining the proper relationship to Church authorities, the laity have the right to found and control such associations and to join those already existing. Yet the dispersion of efforts must be avoided. This happens when new associations and projects are promoted without a sufficient reason, or if antiquated associations or methods are retained beyond their period of usefulness. Nor is it always fitting to transfer indiscriminately forms of the apostolates that have been used in one nation to other nations.
Source: Apostolicam Actuositatem (Vatican.va)