The Sandy Hook elementary school shooting has shaken the nation badly. The violent death of twenty elementary school children plus six adult staff members does not easily submit to detached analysis, nor should it. For the enormity, the monstrosity, of the act that ended those lives is not mere emotional window dressing for raw and barbaric facts, but is of the essence of what the incident was.
The agony of the parents of those children will not quickly fade. For them the days will never be quite as bright again. To a lesser extent everyone in the nation has been permanently affected by the tragedy. It was an event that was at once irrational and horrific, and of the kind that will leave a mark of permanent disturbance in all who partake of sanity.
This is the situation we confront, and it is certain that something should be done about it. We can’t seem to reach consensus on what should be done, but we all know something must be done. What we will decide to do will probably result in some sort of firearm restriction. Magazine capacity, which is what impacts the number of rounds that can be fired without a reload, will doubtlessly be the target.
Of course, legislation on magazine capacity won’t guarantee an end to similar tragedies. The Oklahoma City bombing was accomplished with a home made bomb utilizing fertilizer.  What’s more, underground markets for contraband are what organized crime is all about. Such social horrors as heroin and methamphetamines have been illegal for some time now.
Still, something will be done because something must be done. While the issue will be argued stridently, the something that can be expected is some form of firearms restriction. It can be expected that the constitutional aspect of the question will be given significant attention elsewhere. The focus here will be what, if anything, Catholic social teaching has to say on the matter.
Interestingly, the United States Conference of Catholic Bishops (USCCB) has called for the eventual elimination of handguns from American society.  That is not directly pertinent to the issue at hand since the Sandy Hook victims were not killed with a handgun , but it gives a hint that Catholic social teaching is not going to adopt the positions of the National Rifle Association. Moreover, while statements that are issued by the USCCB do not have magisterial authority (bishop’s conferences do not have the teaching authority of the College of Bishops ), there would be some hubris involved in asserting without proof that the USCCB has uttered any heresy in this connection.
There are two features of Catholic teaching that are pertinent here. The first is that Catholic teaching is pro-life. Whatever will tend to save human lives will be favored by Catholic social teaching, and whatever will tend to cause human deaths will be disfavored. The second is that every person has both the right and the duty to defend his own life and the lives of those he is responsible for, and does not violate the commandment against murder if he takes the life of the aggressor when necessary to do so while engaged in such defense. 
Given these factors for consideration, it seems that a total ban on civilian ownership and possession of firearms would be a counterproductive overreach. Because of the facility of organized crime in supplying contraband, such a ban would not eliminate firearms. Law abiding people could be rendered defenseless in their own homes against individuals immune to the wisdom of pacific precepts. This disadvantage would work disproportionately against the poor, who are more likely to live in crime infested areas. It is easy to see how, given the state of American society, a total ban could cause more deaths than it would save lives.
But this argument for private firearm possession is rooted in legitimate defensive needs, and begins to lose force when the subject turns to high capacity rifles. Even if the arguments in favor of concealed carry are conceded, rifles don’t serve that purpose at all, and it takes a prodigious imagination to conceptualize a circumstance where a rifle that takes detachable thirty-round magazines will be necessary for home defense. While there would be still be a black market for high capacity rifles, it would be criminal street gangs and drug dealers who would have access to that market more than mentally disturbed individuals who would be likely to take such weapons to elementary schools.
People of good faith will differ as to where the lines should be drawn, but it seems clear that the Christian democratic position on this issue is not to be found at the extremes. Neither the needs of legitimate self-defense nor the concerns of public safety should be disregarded. Both wisdom and compassion are called for as we chart our national policy on firearms. It is to be hoped that the national dialogue on the question will be characterized by civility.