In one instance of my occasionally playful priestly formation, several students participated in a mock excommunication of one student held in contempt. A fellow wearing his paper miter stood at a table with bell, book and candle. The accused was summarily sentenced by turning the candle over, expunging its flame. Someone even turned off the lights. The theatrics lasted maybe a full five minutes, and then all was forgiven and forgotten with hearty laughter and handclaps to the back. It was an innocent affair that garnered some scoffs and much mirth, and I suppose that our scandalized professors, had they found out, would have chuckled as well—just not in the presence of students.
But excommunication itself is a serious business. Society has always held as a practice of punishing the guilty and protecting the innocent with a kind of exclusion over a serious crime. In the Old Testament, God formalized this public censure with the penalty that the guilty are no longer free to participate in communal life: ‘Cursed is he who does not confirm the words of this law by doing them.’ And all the people shall say, ‘Amen.' (Dt. 27:26) This same penalty carried over into the New Testament and beyond with the same authority: “But even if we, or an angel from heaven, should preach to you a gospel contrary to what we have preached to you, he is to be accursed!” (Gal. 1:8) Excluding former members from participating in the religious life of the faithful was intended as redemptive or restorative discipline and not a punitive practice.
Abuses crept in when excommunication became politicized in the medieval ages. Eastern and Western Catholic churches even excommunicated each other!  Reaction to abuses led to a clarification still in effect today, that one can be formally cut off from the life of grace through the sacraments either by trial (sententiae ferendae) or an automatic process (latae sententiae) incurred by the fact that particularly egregious sins specified by the Church are knowingly and freely committed. Of the nine specified sins now noted in canon law, one is procuring an abortion (canon 1398). 
Until research was undertaken for this article, I thought that latae sententiae included politicians who promoted abortion through unjust policies or laws. A careful reading of the law condemns only those "actually procur[ing] an abortion.” But Cardinal Ratzinger (now Pope Benedict XVI) explained that there is a moral decrepitude that needs to be condemned, even if suspension of the sacraments doesn’t automatically take place. He argues that politicians who persistently and publicly reject the Church’s teaching on abortion seriously harm communion with the Church and should be denied Holy Communion.
“The Church teaches that abortion or euthanasia is a grave sin. The Encyclical Letter Evangelium vitae, with reference to judicial decisions or civil laws that authorize or promote abortion or euthanasia, states that there is a "grave and clear obligation to oppose them by conscientious objection. [ . . . ] In the case of an intrinsically unjust law, such as a law permitting abortion or euthanasia, it is therefore never licit to obey it, or to ‘take part in a propaganda campaign in favour of such a law or vote for it’" (no. 73) . . . .
“Regarding the grave sin of abortion or euthanasia, when a person’s formal cooperation becomes manifest (understood, in the case of a Catholic politician, as his consistently campaigning and voting for permissive abortion and euthanasia laws), his Pastor should meet with him, instructing him about the Church’s teaching, informing him that he is not to present himself for Holy Communion until he brings to an end the objective situation of sin, and warning him that he will otherwise be denied the Eucharist. 
However, there is another canon law which states that Catholics who “obstinately persist in manifest grave sin, are not to be admitted to Holy Communion” (Canon 915). And in the scandalous case of Nancy Pelosi, her archbishop elicited an interdiction that she not receive communion until she sacramentally confesses her sin and manifest contrition by no longer actively supporting abortion. That the pope would support Pelosi and scorn Cordileone’s actions in practice if not in name, is an ongoing scandal and source of confusion for believers and non-believers world-wide. Archbishop Burke offers this strong criticism:
“No matter how often a Bishop or priest repeats the teaching of the Church regarding procured abortion, if he stands by and does nothing to discipline a Catholic who publicly supports legislation permitting the gravest of injustices and, at the same time, presents himself to receive Holy Communion, then his teaching rings hollow.” 
For the sake of Pelosi and politicians like her, not to mention the countless souls under their influence, we must pray, and encourage others to pray, that the heart of the pope takes seriously the Church’s laws and practices, lest he and the blatant sinners he could have influenced for the better be the ones God holds in contempt.