The sixth precept of Church (as recorded in some lists of precepts, including that as found in The New Saint Joseph Baltimore Catechism), is “To observe the laws of the Church concerning marriage.” Though the Catechism of the Catholic Church does not include this precept in its list within paragraphs 2041-2043, that this precept is still recognized by other sources may be simply to emphasize the necessity for each to live their vocation in the most proper way – especially in reference to the dignity and sanctity of the marriage vocation.
A first point to make is that while the precept expresses the keeping of the laws of the Church concerning marriage, the precept applies to all people to live their lives in a way of upholding of the laws of marriage. For while the particular vocation of marriage is lived in the specific way of union and communion between a man and a woman, it belongs to all of us to uphold the dignity of marriage by respecting and promoting the true good of the married life, both in word and in especially in how we live.
What are these laws of marriage that all of us are to uphold? The laws of marriage begin with the definition of marriage itself as found in the Code of Canon Law, canon 1055, paragraph 1: “The matrimonial covenant, by which a man and a woman establish between themselves a partnership of the whole of life and which is ordered by its nature to the good of the spouses and the procreation and education of offspring, has been raised by Christ the Lord to the dignity of a sacrament between the baptized.” Further (as we will see when covering the sacrament of matrimony), to uphold the laws of marriage means that any and every Catholic who seeks to enter into marriage is to be married in the Catholic Church according to the ritual form of the Church – which includes being in the presence of the authorized witness of the Church (the ordained minister) and two other witnesses. Finally, observing the laws of marriage includes avoiding any and every act that weakens, undermines, or destroys the nature of the marital union: including such actions as adultery, every form of infidelity (including such things as use of pornography and acts of self-gratification), and the use of contraceptives/sterilization, along with acts such promiscuity and/or cohabitation by the non-married.
Acknowledging again that the precepts give the minimum required for growth in the love of God and in virtue, the keeping of the laws of marriage by all peoples both safeguards the sacred and sacramental nature of marriage (as a symbol of God’s love for His Church, through the mutual love and fidelity of husband and wife) and opens us all to greater faith in how God wishes to bless us, both the married and the unmarried. For when we hold in reverence the laws of marriage, seeking to live the proper way of chastity (in fidelity to one’s spouse with openness to life, and/or in living the continence proper to one’s own vocation), God Himself blesses us with graces to become all the more who He made us to be in loving Him and in loving our neighbor as self in an “integrated” way. Such integration loves every person according to “who” they are and in right relationship according to one’s own state in life. To that end, we grow in the virtues of faith (as a way of trusting in God at work in our lives), in hope (of eternal life), and in love (as true self-giving charity), all the while upholding and respecting the most beautiful communion of persons in the Trinity, which is symbolized in the communion of a man and woman in marriage.
For further reading: In the Catechism of the Catholic Church, the paragraphs on the Sixth Commandment (2331-2400) and the Ninth Commandment (2514-2533) provide key insights into keeping this precept.