The short answer is no, remarriage after annulment is morally okay.
The Catholic Church does not acknowledge divorce. In the Catholic mindset, marriage is not merely contractual, but sacramental. It is a permanent spiritual union formed by God, and it makes no more sense to speak of a couple becoming un-married than of a person becoming un-baptized. A divorce, the purpose of which is to dissolve an existing marriage, must then be quite impossible. This is why remarriage after divorce is considered to be adulterous; though a person may have parted ways with their first spouse, they are still married in the sacramental sense, and therefore bound to be faithful to each other according to the prescriptions of Christian marriage.
Remarriage after annulment, however, has totally different moral implications, because divorce and annulment are fundamentally different things.
What is Annulment?
Annulment is not a “Catholic divorce.” The process should not be the first recourse if difficulties develop. Rather than seeking to dissolve a marriage, annulment is a process, governed by a tribunal, which takes the position after an extensive review that the marriage was never fully sacramentally valid. If it was not a valid marriage, the spouses are not bound to each other by a covenant with God. The Church may declare the marriage null, and both spouses are free to remarry.
What Happens in Marriage?
When a couple marries in the Catholic Church, they are bound both legally and sacramentally. They sign a marriage contract acknowledged by civil authorities granting them legal married status when they file for taxes, qualification as next of kin, joint ownership of property, etc. During the ceremony, they are also make sacramental vows before God and their community to regard each other according to the precepts of marriage, which are indissolubility, fidelity, and fertility. This means that their union is permanent, exclusive to the two of them, and open to the possibility of bearing children.
Divorce affects only the legal stipulations of a marriage, and it is not necessarily immoral for a married couple to contract one. None of the precepts of marriage state that a married couple must live together or have a joint bank account. If a relationship is abusive or unhealthy, especially if the safety of oneself or one’s children is threatened by proximity to the other spouse, it is absolutely permitted for the spouses to separate, and a legal divorce might be a component of such a separation.
In this situation the legal aspect of the marriage is dissolved, but the sacramental aspect is still in effect. Therefore, the spouses are still bound to the precept of exclusivity and cannot marry again without committing adultery. The Church acknowledges that such situations are difficult and painful, and maintains that reconciliation is the ideal solution if it can be achieved.
What if Spouses No Longer Are Reconcilable?
This is where annulment still offers a possibility that the spouses may be able to remarry without sin.
When a couple applies for an annulment, an investigation commences into the circumstances of their relationship at the time of the wedding. The investigation looks purely at one aspect: did a valid sacramental marriage actually take place? What canon law grounds or other aspects would apply to a possible annulment? For instance, if a valid marriage takes place but later the couple grows apart, or one or both spouses are unfaithful, this alone is not at all grounds for an annulment.
Criteria for Annulment
To prove that a marriage is invalid, the couple must provide evidence that falls into one of a few basic categories.
One or both spouses did not freely consent to the marriage.
Because it is a personal covenant with the other spouse and with God, clear and conscious consent is absolutely indispensable to the validity of a marriage. The amount of spiritual investment presupposed in the very concept of marriage would be impossible without it. For this reason, any marriage is invalid if one or both spouses was not of sound mind at the time of the wedding, did not understand the nature of the commitment, was not fully conscious, or was compelled by some exterior force.
The couple did not intend to follow the Catholic precepts of marriage.
Grounds of this sort might include evidence that the couple procured an abortion prior to the births of other children, indicating that they were not open to the precept of fertility. An extramarital affair could also render the marriage invalid if taking place at the time of the wedding, or if one or both of the spouses did not intend the marriage to be exclusive. Also, both spouses must understand the marriage is till “death do you part.” The marriage is indissoluble. Making a prenuptial agreement, for instance, admits a possibility the marriage could end and so is not permitted. No one must be held to promises that they never made, and the vow to follow these precepts must be conscious and sincere, or the marriage is not sacramentally valid.
The couple agreed to marry for reasons other than a wish to be married to each other.
Into this category fall cases in which the couple did fully consent to marry each other, and perhaps even intended to follow the precepts of marriage, but came to this decision for the wrong reasons. For example, someone may have decided to get married so that they could come into an inheritance, or to obtain legal residence in a particular country. Marriages entered into mainly for reasons other than a vocation to live together in the divine office of matrimony are not considered to have the full validity of the sacrament.
One or both spouses deceived the other previous to the marriage on an issue that would have affected their decision to get married.
For instance, if a spouse concealed infertility before the marriage and the other spouse married them believing that they could have children together, then they might submit that as evidence that they entered into the marriage on false pretenses.
Other such unwelcome surprises might include a preexisting venereal disease, previous incarceration, and a great many others. One stipulation to keep in mind is that this applies only to facts that were fully established at the time of the marriage. A wife may consider herself deceived on a grave issue if she marries a man who claimed to be a brain surgeon and turns out to be a drug smuggler, but not if she marries a man who said he was going to go to medical school to become a brain surgeon but never graduates. All commitments are made in the awareness that the future is uncertain, and a covenant does not disappear if things turn out differently than one hoped.
A precise and comprehensive account of legitimate grounds for annulment can be found in the Code of Canon Law.
All these grounds for invalidity concern the circumstances at the time of the wedding. If a couple knowingly consented to marry each other, was undeceived about the relevant facts of each other’s lives, and intended to follow the precepts of marriage in order to pursue a vocation in the office of matrimony, the marriage is valid no matter what goes wrong after that.
Many Catholics married in the Church apply for annulments when they have given up on the possibility of repairing their marriage and wish to remarry, sometimes years after separation and divorce. The annulment process can be rather prolonged, but is not usually as arduous as some believe it to be. Each case is investigated by a tribunal with three judges. Once the facts are established, the tribunal will either issue or deny a declaration of nullity based on their determination of the marriage’s validity.
In 2015, Pope Francis helped to streamline the process by placing responsibility for processing annulment applications on the shoulders of the local bishop and creating an avenue by which the more clear-cut cases can be processed through him directly. Tribunals were also encouraged to issue decisions promptly and free of charge whenever possible. These changes do not expand acceptable grounds for annulment; instead Pope Francis has made some purely logistical adjustments so that the many Catholics who have divorced and remarried outside the church will not be held back from returning to communion by a daunting bureaucracy.