If the U.S. government told the Catholic Church it must give Holy  Communion to such politicians that would be a violation of the Constitution, not the other way around. The Church's right to its own internal governance according to its own teachings is precisely what the Constitution protects! The First Amendment states, 

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.

This amendment ensures that the U.S. Congress will not establish a religion as the religion of the United States. In England the established religion was and is Anglicanism, as it was in Virginia and other of the American colonies. Many state constitutions adopted the same provision, although established churches with special rights persisted into the 1800s in some states. These anti-establishment clauses protect the freedom of believers and their Churches, Synagogues, Mosques and Temples from the interference of the Federal and state governments.

2. Isn't it contrary to the freedom of conscience of Catholic politicians to condition their participation in Holy Communion to the Church's stance on moral issues?

The Church is the sacrament of salvation which continues the redemptive mission of Jesus Christ in the world. He does not force salvation on anyone. People freely choose to enter or remain in the Church. They likewise freely choose to recite the Nicene Creed at Sunday Mass, in which they affirm the divine institution and authority of the Church: I believe in One, Holy Catholic and Apostolic Church. To not hold Catholic politicians to the solemn commitments of the faith which they have made would be to say that freedom of conscience means being able to freely make and break solemn commitments made to God.

So, in the end the Catholic politician is free to disagree with Church teaching, vote as he or she pleases, and the Church is likewise free to refuse Holy Communion to those who are unworthy.

3. In a pluralistic society isn't it better, however, if a politician makes up his own mind, without being sectarian and advancing only the views of his own religion?

First, in no other matter, save religion, is a politician expected to leave his personal beliefs at the door to civil office. Yet, in no other matter, save religion, is the right to personal belief protected by the Constitution, for citizens and politicians alike.

Secondly, some worldview is going to be the foundation of everyone's thinking, giving it coherence and direction. It might be atheism, agnosticism, scientism, communism, feminism, nihilism or simple egotism, but, for most people it is religion. It determines their conscience and, as a consequence, their decisions and actions. To ask them to set it aside, or for them to set it aside, may have the appearance of pluralism but in reality it calls into question their  integrity. If something so important can be set aside, how can they be trusted to hold to other less important principles.

Sadly, opinion polls show that the public has a low confidence in politicians, believing that they flip-flop according to the political winds. Nothing could be more disastrous for a democracy. Far better to have a man of known principles in office, even if they are not entirely one's own, than a man of no principle. The ancient political philosophers, such as Plato and Cicero, correctly identified the weakness of democracy, its tendency to mob mentality over principle. For democracy to work the principles of politicians need to be known and their word be trustworthy.

4. If that is the case, why not also withhold communion from Catholic politicians who voted in favor of the Iraq war or who favor the death penalty? Aren't these Catholic teachings as well?

There are indeed Catholic teachings on the subject of war and on the subject of capital punishment, and the principles regarding them  have the same authority as the teaching on abortion. In all life issues the first principle is the same, "one may not take the life of an innocent human being." In the case of abortion the child is always innocent, therefore, it is always intrinsically evil to take the life of the unborn, whether a fetus or an embryo.

However, neither war nor capital punishment are intrinsically evil. On the contrary, the authority for war and for capital punishment are inherent in the right of self-defense of the individual and of the state. Naturally, there are principles governing the just use of this right which must be accepted by Catholics. However, Catholics can, and do, disagree among themselves as to the application of these principles to particular cases. The Pope's strong words against both modern war and the use of capital punishment except in rare circumstances have not changed Catholic teaching on the right of justified self-defense, even with deadly force, nor could they. Rather, he has argued for a culture of life that eschews violence except when absolutely necessary. In this I believe he is prudentially right if we are to reverse the culture of death in our world.

So, on the one hand there is an intrinsic moral evil, abortion, which kills a million in the U.S. each year and tens of millions worldwide, and on the other hand there is war, possibly unjustified, which has killed thousands. There is really no comparison.

5. What about social programs? Shouldn't Catholic politicians uphold the Catholic position on the social agenda in economics, the environment, labor unions, etc?

The assumption is faulty, as there is no official Catholic position, except at the level of principles. Yes, the Church favors a social net to protect those who cannot protect themselves. Likewise it favors protecting the environment, labor laws that protect workers, the right to organize unions etc.. These papal and conciliar teachings tell us what a just society should be. However, they don't tell politicians exactly how to attain it, that is, what balance of public versus private services, of state control versus free market, of capital versus labor, and so on on, best achieves the goal. The Church provides the principles, but their application is a matter of political prudence, and their success depends on factors often outside of human control.

In the end the achievement of political consensus on social policies is generally justified. However, this is not true when the matter in question is an objective evil. No one may ever do evil that good may come of it.

6. Why are the bishops doing this now, rather than having done it all along?

I suppose they thought that they could win such politicians with argument. In fact, the trend has been entirely the other way, with some Catholic politicians taking more and more extreme positions despite the clear teaching of the Church. In the process, the scandal of their public positions at odds with divine law has won many of the Catholic laity to those positions. Without the strong medicine of ecclesiastical sanctions this trend appears irreversible.

7. Where did this law come from that is being invoked to withhold Communion?

It comes from the divine law. Holy Communion is Jesus Himself, God-made-man. By divine law, directly revealed in Sacred Scripture, the Body and Blood of the Lord must be received worthily, otherwise the person condemns themselves (1 Cor. 11:27-32).

Secondly, it comes from Church teaching and law. The Council of Trent formally taught that one must receive Holy Communion worthily, that is, in the state of grace (Decree on the Holy Eucharist, Ch. VIII). The 1917 Code of Canon Law and its 1983 revision, both oblige a Catholic who is conscious of grave sin to go to confession before receiving Holy Communion and provides that the minister of Communion not admit those to Holy Communion who are guilty of manifest grave sin.

8. What does Church law say specifically?

First, most people who have need of the sacrament of confession are not public sinners. Their sins are known to themselves, the persons they may have sinned against, and others who may have found out, such as family and friends. Church law provides that they are responsible for going to Confession or refraining from Communion themselves (c. 916). Such persons cannot be publicly refused Holy Communion if they publicly ask for it, such as by coming forward at Mass.

Canon 912   Any baptized person who is not prohibited by law can and must be admitted to Holy Communion.

Canon 916 A person who is conscious of grave sin is not to celebrate Mass or to receive the Body of the Lord without prior sacramental confession unless a grave reason is present and there is no opportunity of confessing; in this case the person is to be mindful of the obligation to make an act of perfect contrition, including the intention of confessing as soon as possible.

However, the Code of Canon Law also provides,

Canon 915   Those who are excommunicated or interdicted after the imposition or declaration of the penalty and others who obstinately persist in manifest grave sin are not to be admitted to Holy Communion.

Who are those who must be refused, that is, "are not to be admitted to Holy Communion"? The moral and canonical tradition of the Church explains it as those who are "publicly unworthy" (1917 Code c. 855, 1), that is, who despite having been warned have not repented and repaired the public scandal ("obstinately persist") in some public condition of grave sinfulness ("manifest grave sin"). This certainly applies to anyone, and not just politicians, who publicly and unrepentantly promote and advance grave evils, such as abortion, which the Church has formally identified as such.

Apologetics - Doctrine - Canon Law - Eastern Churches - General - History - Liturgy - Moral
NFP - Philosophy - Pro-Life - Scripture - Spiritual