Catechism of the Catholic Church
1646 By its very nature conjugal love requires the inviolable fidelity of the spouses. This is the consequence of the gift of themselves which they make to each other. Love seeks to be definitive; it cannot be an arrangement "until further notice." The "intimate union of marriage, as a mutual giving of two persons, and the good of the children, demand total fidelity from the spouses and require an unbreakable union between them." 157
1647 The deepest reason is found in the fidelity of God to his covenant, in that of Christ to his Church. Through the sacrament of Matrimony the spouses are enabled to represent this fidelity and witness to it. Through the sacrament, the indissolubility of marriage receives a new and deeper meaning.
1648 It can seem difficult, even impossible, to bind oneself for life to another human being. This makes it all the more important to proclaim the Good News that God loves us with a definitive and irrevocable love, that married couples share in this love, that it supports and sustains them, and that by their own faithfulness they can be witnesses to God's faithful love. Spouses who with God's grace give this witness, often in very difficult conditions, deserve the gratitude and support of the ecclesial community. 158
1649 Yet there are some situations in which living together becomes practically impossible for a variety of reasons. In such cases the Church permits the physical separation of the couple and their living apart. The spouses do not cease to be husband and wife before God and so are not free to contract a new union. In this difficult situation, the best solution would be, if possible, reconciliation. The Christian community is called to help these persons live out their situation in a Christian manner and in fidelity to their marriage bond which remains indissoluble. 159
1650 Today there are numerous Catholics in many countries who have recourse to civil divorce and contract new civil unions. In fidelity to the words of Jesus Christ - "Whoever divorces his wife and marries another, commits adultery against her; and if she divorces her husband and marries another, she commits adultery" 160 the Church maintains that a new union cannot be recognized as valid, if the first marriage was. If the divorced are remarried civilly, they find themselves in a situation that objectively contravenes God's law. Consequently, they cannot receive Eucharistic communion as long as this situation persists. For the same reason, they cannot exercise certain ecclesial responsibilities. Reconciliation through the sacrament of Penance can be granted only to those who have repented for having violated the sign of the covenant and of fidelity to Christ, and who are committed to living in complete continence.
1651 Toward Christians who live in this situation, and who often keep the faith and desire to bring up their children in a Christian manner, priests and the whole community must manifest an attentive solicitude, so that they do not consider themselves separated from the Church, in whose life they can and must participate as baptized persons:
They should be encouraged to listen to the Word of God, to attend the Sacrifice of the Mass, to persevere in prayer, to contribute to works of charity and to community efforts for justice, to bring up their children in the Christian faith, to cultivate the spirit and practice of penance and thus implore, day by day, God's grace. 161
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.