The apostolate is not something reserved to clergy and religious. It never was. Long before Vatican II — which, according to a strange mythology, first asserted the importance of the laity in propagating the Catholic message — Saint Vincent Pallotti made layfolk members of his “Union of the Catholic Apostolate.” And in doing so, he was made no claim to originality.
The right and obligation of the laity to work for the spread of the Catholic faith is here given in the Church’s Code of Canon Law:
Can. 225 §1 Since lay people, like all Christ’s faithful, are deputed to the apostolate by baptism and confirmation, they are bound by the general obligation and they have the right, whether as individuals or in associations, to strive so that the divine message of salvation may be known and accepted by all people throughout the world. This obligation is all the more insistent in circumstances in which only through them are people able to hear the Gospel and to know Christ.
§2 They have also, according to the condition of each, the special obligation to permeate and perfect the temporal order of things with the spirit of the Gospel. In this way, particularly in conducting secular business and exercising secular functions, they are to give witness to Christ.
Note this sentence: “This obligation is all the more insistent in circumstances in which only through them are people able to hear the Gospel and to know Christ.” The Code does not specify the circumstances that render the laity the only ones capable of making the divine message of salvation known and accepted. It is possible, nay plausible, that there could be a respectable number of priests in a given place, but that their own internal “circumstances” make them incapable of helping people to know Christ or the Gospel. Modernism has done its damage.
Catholic faithful! You have your mandate, and that from the Church’s highest authority. Learn the faith and pass it on.