Dear ej,
The Catechism of the Catholic Church was published just before the current commotion about gay marriage erupted. Number 2360 states: “Sexuality is ordered to the conjugal love of man and woman. In marriage the physical intimacy of the spouses becomes a sign and pledge of spiritual communion. Marriage bonds between baptized persons are sanctified by the sacrament.”
In number 1919 it states: “…It is the role of the state to defend and promote the common good of civil society, its citizens, and intermediate bodies.”
In number 2358 it states: “….Basing itself on Sacred Scripture, which presents homosexual acts as acts of grave depravity, tradition has always declared that ‘homosexual acts are intrinsically disordered.’ They are contrary to the natural law. They close the sexual act to the gift of life. They do not proceed from a genuine affective and sexual complementarity. Under no circumstances can they be approved.
If the Catechism were to add a section on gay marriage, you can be sure that it would not consider such attempts at marriage to be in the interest of the common good—which is what governments should be about.
Fr. Vincent Serpa, O.P.