Illinois Governor Pat Quinn, supposedly a Catholic, plans to give an award to a pro-abortion PAC. The bishops rightly blasted him for this. In several places I have seen the claim that he (and politicians like him) have already excommunicated themselves under what is called latae sententiae excommunication.
Whenever someone tosses out the “E”-word, I go to canon lawyer Ed Peters. He has recently posted on the bishop’s response here: http://canonlawblog.blogspot.com/2011/11/gov-pat-quinn-and-illinois-catholic.html. But from awhile back he also posted an article explaining that the case that pro-abortion politicians have triggered the Canon law covering LS excommunications regarding abortion (Canon 1398) is very weak. Read it here: http://canonlawblog.blogspot.com/2007/05/case-for-applying-canon-1398-to.html