Raymond Card. Burke, Prefect of the Apostolic Signatura, is probably the expert on can. 915.
I picked this up from EWTN:
Cardinal says no communion for Irish politicians who support abortion
As the Irish parliament considers legalizing some abortions, Cardinal Raymond Burke says that local Catholic politicians who support the procedure should be refused Holy Communion in hopes of inspiring their conversion.
“There can be no question that the practice of abortion is among the gravest of manifest sins,”Cardinal Burke told the Irish newspaper Catholic Voice in an interview published Feb. 1.
Once “a Catholic politician has been admonished that he should not come forward to receive Holy Communion,” the cardinal added, “as long as he continues to support legislation which fosters abortion or other intrinsic evils, then he should be refused Holy Communion.”
The American cardinal heads the Apostolic Signatura, the Vatican’s highest legal tribunal that rules on canon law.
Cardinal Burke said that the local bishop and parish priests [and parish priests] must ensure that Holy Communion is properly received to avoid “the grave sin of sacrilege” from those like Catholic politicians who receive Communion in spite of “grave moral evil.” The bishops and clergy must also prevent the “scandal” caused by this kind of reception because it “gives the impression that the Church’s teaching on the intrinsic evil of abortion is not firm.” [and not only abortion]
The cardinal said Catholic politicians have the duty to support all legislation that will “most reduce the evils which attack human life and the integrity of marriage.” [not only abortion]
Politicians cannot vote for any legislation which would confirm or advance “evil,” but a politician may support legislation to reduce such evils if he acknowledges these evils and the need for his voters to work to eliminate them.
Cardinal Burke stressed that the Catholic Church’s rules on the need to receive communion worthily are based on Christians’ relationship with Jesus Christ.
Someone who persists in “manifest grave sin” should not receive Holy Communion “because of his love of our Lord and his sorrow for the grave sin which he is committing against our Lord and His Holy Church.”
Recognizing this “grave offense” against God will “most inspire a conversion of heart” in Catholic politicians who support abortion, the cardinal said. He cited St. Paul’s admonition in the First Letter to the Corinthians that those who receive communion unworthily “eats and drinks judgment upon himself.”