The Church does not have a definitive teaching on the private ownership of firearms. However, the Church does support the right to possess firearms for the legitimate defense of the common good of the family.
Unfortunately, however, it is impossible to ban all kinds of small arms and light weapons. In a world marked by evil . . . the right of legitimate defense by means of arms exists. This right can become a serious duty for those who are responsible for the lives of others, for the common good of the family or of the civil community. This right alone can justify the possession or transfer of arms. (Holy See Delegation to the International Conference on Illicit Trade in Small Arms and Light Weapons in all Its Aspects, July 11, 2001)