Mostly in responce to Everyman’s orginal question:
Yes, the Church views the truth about gay marriage as something that accesable to all through reason, and therefore is something that all societies should uphold truths about, through laws if necessary.
This is because of the Church’s postion on something called Natural Law. I’m not sure how fimilar you are with this, but here’s kinda a brief rundown in relation to the orginal question. There are basic universal truths that are known by everyone, you can’t not know these things. That is because these truths are written into our very being. You see these truths across all cultures, don’t muder, marriage is special, don’t lie to prevent justice, etc… unforunately, while it in escapable that we “know” these things, understanding and applying them are very different. Here, is where we use reason, and while it very possible for all men to use reason and come to a correct understanding of the truth, not all men do. Hence, the Dali Llama, without being Christian, or having the aide of Christian Revelation, has discovered that marriage should be hetrosexual, but has fallen into error about how to apply this society.
Some truths about marriage are things that are knowable without the aide of Revelation, including that marriage should be hetrosexual. (See jmcrea’s first paragraph), and therefore its applicatable to all societies. So, yes, the Church does maintain that this is one of her teachings that society should enforce, but not b/c “we should try to conform our government’s laws to what we as Christians believe to be the moral law of God,” (although this is not a bad thing to do), but rather because this part of the Natual Law that all men follow.
I briefy saw the last link to a Vactian docuement (I didn’t read it) but might I also recommend Vertias Splendor, by our late great Pope, John Paul II. It’s long, and theologically dense, as JP often was, but that document has become the conerstone of moral thought since Vactian II. Here is a link:
vatican.va/edocs/ENG0222/_INDEX.HTM
Since it long, here are some texts I would recommend:
On Natural Law: 35-46
and broadly on Homosexuality: 47-53 (really on biologism, but it relates)