104 Though We desire this unceasing prayer to rise to God from the whole Mystical Body in common, that all the straying sheep may hasten to enter the one fold of Jesus Christ, yet We recognize that this must be done of their own free will; for no one believes unless he wills to believe. Hence they are most certainly not genuine Christians who against their belief are forced to go into a church, to approach the altar and to receive the Sacraments; for the "faith without which it is impossible to please God" is an entirely free "submission of intellect and will." Therefore, whenever it happens, despite the constant teaching of this Apostolic See, that anyone is compelled to embrace the Catholic faith against his will, Our sense of duty demands that We condemn the act. For men must be effectively drawn to the truth by the Father of light through the spirit of His beloved Son, because, endowed as they are with free will, they can misuse their freedom under the impulse of mental agitation and base desires. Unfortunately many are still wandering far from the Catholic truth, being unwilling to follow the inspirations of divine grace, because neither they nor the faithful pray to God with sufficient fervor for this intention. Again and again We beg all we ardently love the Church to follow the example of the Divine Redeemer and to give themselves constantly to such prayer.
Source: Mystici Corporis Christi (Vatican.va)