The question of who should, or who should not, receive Holy Communion in the Catholic Church is obviously an important matter and is currently a hot topic within the Catholic Church. This is not least because of the comments of various Cardinals about whether re-married divorcees should be permitted in some circumstances to receive Holy Communion despite them still living in sin (for the Church upholds Christ's teaching that there cannot be a re-marriage after 'divorce'/separation). In the Ordinariate it is a live issue especially when our brother and sisters of the Anglican communion sometimes come to the altar rail wanting to receive the Catholic Eucharist. It can seem to some harsh that they are denied Communion, and it can seem like legalism when they are told the Canons of the Church do not permit them to receive.
Merely explaining the Church's Canons on the matter is obviously an inadequate and usually unhelpful response for these situations. What we need to do is get behind the reasons for the Canons (because Canon Law springs from Church teaching and is not an arbitrary rulebook) so that we clearly understand why and then can help pastorally, those who find it a difficult discipline.
In the following excellent article we are reminded that the Church teaches not only of the benefits of receiving Holy Communion (the grace of the Sacrament) but also of the dangers! The dangers of the Sacrament are what many people are forgetting in the discussion. Yes the Eucharist has wonderful and awesome benefits of grace, that of course we want all people to receive - including and perhaps especially those in grave sin. But the Church teaches that there are dangers in receiving the Eucharist in an unworthy manner. Because the Eucharist is Christ Himself (body and soul), the benefits and dangers are extreme! It is a truly life and death issue.
Please read this very thoughtful and helpful article in order to get to grips with the real issues. That way you can be better equipped to enter any discussion you come across about this matter.
Holy Communion - a matter of life and death