"The reception of the Body of Christ when one is publicly unworthy constitutes an objective harm" to the church and to the faithful who obey it, said a declaration issued by the Pontifical Council for the Interpretation of Legislative Texts.
The only situations in which such couples may receive the Eucharist are if they separate or if they are committed to refraining from sexual relations, said the declaration dated June 24 and Thursday at the Vatican.
The declaration was signed by Archbishop Julian Herranz, council president, and Bishop Bruno Bertagna, council secretary.
Reaffirming the prohibition of Communion for divorced and civilly remarried Catholics, the declaration chastised "some authors" who have tried to show that the prohibition is not called for by canon law.
According to the canon in question, those "who obstinately persist in manifest grave sin are not to be admitted to Holy Communion."
Because divorce is not recognized by the church, civil remarriage is not recognized either, and the couple is considered to be living in adultery.
The Vatican said it issued the new declaration because some theologians "using a variety of arguments" had claimed there were loopholes in church rules that would allow those who divorce and remarry to receive Communion.
Some "authors," the declaration said, referring to the theologians and others, have argued that simply being divorced and civilly remarried is not enough to invoke the law.
For example, the declaration said, these authors have said, "given that the text speaks of those who 'obstinately' persist in that sin, it would be necessary to verify an attitude of defiance on the part of an individual who had received a legitimate warning from the pastor."
"The phrase 'and others who obstinately persist in manifest grave sin' is clear and must be understood in a manner that does not distort its sense so as to render the norm inapplicable," Herranz wrote.
Catholics in the United States, Germany, and elsewhere have been pressing the Vatican to loosen the restriction.
The statement also said the restriction is based on "divine law" and cannot be modified.
In addition, the declaration reaffirmed earlier Vatican statements that priests should try to explain in private to divorced and civilly remarried Catholics why they cannot receive the Eucharist, avoiding "public denial of Holy Communion."
"In those situations, however, in which these precautionary measures have not had their effect or in which they were not possible, the minister of Communion must refuse to distribute it to those who are publicly unworthy," the statement said.
It stressed that the declaration did not contradict the desire for those Catholics to participate in church life "in the many forms compatible with their situation that is already possible for them."
In the Catholic Church, civil divorce does not entail exclusion from the sacraments. But a person is excluded if he or she remarries outside the church while bound in the church's eyes by a valid previous marriage.
The declaration was issued by the Pontifical Council for Legislative Texts, taking into account the views of the Congregation for the Doctrine of the Faith and two other Vatican offices.
The document said that affirming the church's teaching on the indissolubility of marriage and on the sacredness of the Eucharist is a sign of "genuine pastoral care" and "authentic concern" for the divorced and remarried.
Explaining the conditions necessary for their return to the Eucharist is the only way to help them undergo "the fullness of that conversion to which all are always invited by the Lord, particularly during this Holy Year of the great jubilee," it said.