It states (from
http://www.law.cornell.edu/constitution/constitution.articleiv.html#section1)
"Article IV
Section 1. Full faith and credit shall be given in each state to the public acts, records, and judicial proceedings of every other state. And the Congress may by general laws prescribe the manner in which such acts, records, and proceedings shall be proved, and the effect thereof.
Section 2. The citizens of each state shall be entitled to all privileges and immunities of citizens in the several states."
The only way to ban same-sex marriage that passes the Constitutional sniff test is to amend the Constitution itself; otherwise, if even one state legalizes it (and sticks to it), EVERY OTHER STATE must respect that.
On a side note, CSPAN2 has the debate on the cloture amendment on right now. So far, the position of the supporters of the amendment seems to be "Well, *we* wouldn't ever marry someone of the same sex, so *no one* should be able to. We just don't like it." They are unable to find any stronger support for their position (like demonstrating how the marriage of a same sex couple hurts anyone.)
Hey, same sex marriage isn't for me, either, but I don't think that is a good enough reason to ban it. I don't like brussels sprouts or country music, but if two freely consenting adults who do like those things want to hook up, I say "go for it - knock yourselves out.
Yeah, this is a bit of a rant. I think this whole thing is the least important hot-button issue of our times (flag-burning has fallen to 2nd). I also think the debate is just an excuse to avoid talking about real issues, like corruption, the war in Iraq (and pending war in Iran), the failure of the Bush Admin to obey the law, etc.