There is a movement on the Catholic internet that is trying to put forth the idea that divorce is a sin and that divorced, but not remarried Catholics should not receive Communion. This is so incorrect. It is yet another of the misunderstandings of Catholic spirituality that is semi-true. St. Augustine decried what he called the "one-book people". These were people who considered themselves experts because they read one book on a subject. The current movement, similar to what St. Augustine decried, is claiming that getting divorced is a sin. They will cite canon law that says the bishop must give the couple permission to divorce otherwise they are in mortal sin.
If this is what Canon Law teaches, then what is wrong with people saying this? What is wrong is that what is missed is that divorce usually is preceded by a host of behaviors and other decisions that are themselves sins. If this part of the marriage is not cared for, then the whole marriage can fall apart. Remember marriage is a vocation.
Let us look at those aspects that can lead to a divorce:
Bari Z. Weinberger writing for the blog at Lawyers.com, cites five reasons for divorce. Adultery is number one. One of the most powerful causes for adultery is when the spouses choose to stop having sexual relationships. A Catholic marriage actually includes sexual intercourse. Spouses that choose not to engage in it, actually are not living a Catholic marriage. Further in such a marriage often one or both spouses will look elsewhere and that is where adultery happens.
Adultery even if the marriage continues can also lead to resentment from lack of forgiveness and is a severe wound on the marriage that needs to be healed on many levels, including the sacramental. Marriages can survive adultery, but a true Catholic marriage that falls into it needs the help of prayer and sacraments, which were probably missing prior. Adultery is not only a mortal sin, it also violates a commandment. I think one would be hard-pressed to rationalize it as anything but mortal. Remember, often the worst sin is to rationalize away sin.
One of the causes of adultery can be falling into a habit of viewing pornography, which is also a mortal sin. A great deal of literature indicates that if a wife finds that her husband is viewing pornography, she can often take it that she lacks something that those woman in the magazines or videos do not. However, they are nothing but fantasies. They do no actually exist. They are at best playing a part they do not live in real life, but the viewer gets lost in this fantasy.
One can expect that many marriages that follow this path or others to divorce have come to the point where engaging in prayer and staying close to the sacraments has long gone by the wayside in one or both of the married couple. But marriage, like priesthood, is a vocation. If the priest who does not pray or take his faith seriously will fall into serious and dangerous sin, how can the married spouses expect not to fall away as well if they don't engage in prayer and stay close to the sacraments. As one spiritual advisor in the seminary warned us: "Do not be a priest who does not pray!" Well the same can be said of the married couple.
St. Paul's admonition to married spouses is not to have the wife become the slave of the husband, but for both to love, respect and serve each other in Christ. They are to serve each other as Christ would serve them. If this is missing in the marriage then this too is an issue.
If one of the spouses is seeking to live the Catholic life, despite the other refusing to engage in it, is that spouse in mortal sin, if the marriage is falling apart even if he or she did all possible to keep it together? No, of course not.
Divorce is often the fruit of behaviors that a serious Catholic couple avoids. If one spouse falls into such behavior, it is an indication that not only something is wrong in the marriage, but also in the sacramental life of the one of both spouses.
Finally, an annulment, which requires a divorce, is granted if after an investigation into the marriage it was found that one or both spouses were unable to enter into the full sacrament of the marriage for various reasons. If a spouse chose not to have children for example, that is grounds for an annulment right there and if they chose not to have children as part of their marriage agreement, then they actually cannot get married in the Catholic Church, it is an impediment. A pre-nuptial agreement is also an impediment to marriage for it indicates no intention to enter into the marriage for life.
The current movement to declare couples seeking a divorce without the bishop's permission to be in mortal sin is misguided. It is further example of a legalistic view of Catholicism. In fact, divorce is often the result of a pattern of sin that needs to be addressed before hand. That is where the issue needs to be focus not after the fact.