CCC 1623: In the Latin Church, it is ordinarily understood that the spouses, as ministers of Christ's grace, mutually confer upon each other the sacrament of Matrimony by expressing their consent before the Church. In the Eastern liturgies the minister of this sacrament (which is called "Crowning") is the priest or bishop who, after receiving the mutual consent of the spouses, successively crowns the bridegroom and the bride as a sign of the marriage covenant.

CCC 1625: The parties to a marriage covenant are a baptized man and woman, free to contract marriage, who freely express their consent; "to be free" means:
- not being under constraint;
- not impeded by any natural or ecclesiastical law.

Canon 1073: A diriment impediment renders a person unqualified to contract marriage validly.

Canon 1083: §1. A man before he has completed his sixteenth year of age and a woman before she has completed her fourteenth year of age cannot enter into a valid marriage.

§2. The conference of bishops is free to establish a higher age for the licit celebration of marriage.

Canon 1084: §1. Antecedent and perpetual impotence to have intercourse, whether on the part of the man or the woman, whether absolute or relative, nullifies marriage by its very nature.

§2. If the impediment of impotence is doubtful, whether by a doubt about the law or a doubt about a fact, a marriage must not be impeded nor, while the doubt remains, declared null.

§3. Sterility neither prohibits nor nullifies marriage, without prejudice to the prescript of canon 1098.

Canon 1085: §1. A person bound by the bond of a prior marriage, even if it was not consummated, invalidly attempts marriage.

§2. Even if the prior marriage is invalid or dissolved for any reason, it is not on that account permitted to contract another before the nullity or dissolution of the prior marriage is established legitimately and certainly.

Canon 1086: §1. A marriage between two persons, one of whom has been baptized in the Catholic Church or received into it and has not defected from it by a formal act and the other of whom is not baptized, is invalid.

§2. A person is not to be dispensed from this impediment unless the conditions mentioned in canon 1125 and canon 1126 have been fulfilled.

§3. If at the time the marriage was contracted one party was commonly held to have been baptized or the baptism was doubtful, the validity of the marriage must be presumed according to the norm of canon 1060 until it is proven with certainty that one party was baptized but the other was not.

Canon 1087: Those in sacred orders invalidly attempt marriage.

Canon 1088: Those bound by a public perpetual vow of chastity in a religious institute invalidly attempt marriage.

Canon 1089: No marriage can exist between a man and a woman who has been abducted or at least detained with a view of contracting marriage with her unless the woman chooses marriage of her own accord after she has been separated from the captor and established in a safe and free place.

Canon 1090: §1. Anyone who with a view to entering marriage with a certain person has brought about the death of that person’s spouse or of one’s own spouse invalidly attempts this marriage.

§2. Those who have brought about the death of a spouse by mutual physical or moral cooperation also invalidly attempt a marriage together.

Canon 1091: §1. In the direct line of consanguinity marriage is invalid between all ancestors and descendants, both legitimate and natural.

§2. In the collateral line marriage is invalid up to and including the fourth degree.

§3. The impediment of consanguinity is not multiplied.

§4. A marriage is never permitted if doubt exists whether the partners are related by consanguinity in any degree of the direct line or in the second degree of the collateral line.

Canon 1092: Affinity in the direct line in any degree invalidates a marriage.

Canon 1093: The impediment of public propriety arises from an invalid marriage after the establishment of common life or from notorious or public concubinage. It nullifies marriage in the first degree of the direct line between the man and the blood relatives of the woman, and vice versa.

Canon 1094: Those who are related in the direct line or in the second degree of the collateral line by a legal relationship arising from adoption cannot contract marriage together validly.

Canon 915: Those who have been excommunicated or interdicted after the imposition or declaration of the penalty and others obstinately persevering in manifest grave sin are not to be admitted to holy communion.

Canon 916: A person who is conscious of grave sin is not to celebrate Mass or receive the body of the Lord without previous sacramental confession unless there is a grave reason and there is no opportunity to confess; in this case the person is to remember the obligation to make an act of perfect contrition which includes the resolution of confessing as soon as possible.

Canon 1142: For a just cause, the Roman Pontiff can dissolve a non-consummated marriage between baptized persons or between a baptized party and a non-baptized party at the request of both parties or of one of them, even if the other party is unwilling.

I would say, then, that a baptized Catholic in a valid, consummated marriage who "divorces" and contracts a new marriage would be committing adultery and not eligible to receive Holy Communion, per Canon Law.

There are abuses.

She immediately married the other guy who was the real cause of the annulment.

I heard a priest preach that John the Baptist would not be put to death today. He would say to Herod, "let's go talk to the marriage tribunal and work this out."