(This is to the OP.) The whole premise of your "legal" argument seems predicated on the presumption that you know what "natural law" is and that somehow the laws of our Republic must, by necessity, be congruent with your personal views of what that "natural law" is. Both premises are erroneous.
If homosexuality is against "natural law," please someone explain to me why hundreds of animal species engage in homosexual behavior. (Google that, I'm new here so I can't post any links yet to support that statement, but it's very easy to find the data on this.)
Incidentally though, it's probably safe to say humans are the only species who make such a big deal of this subject, probably because we're the only ones who feverishly stick our noses into a collection of questionably translated desert scribblings from thousands of years ago which also proscribes such barbaric atrocities as slavery, and bloody animal sacrifices. (See Leviticus chapters 1-9... Have you sprinkled your Ox blood lately?)
In discussing the age old definition of marriage, one man, one woman, since the beginning of time, I love the story of Abraham and Sarai in Genesis chapter 16. When Sarai was infertile, she tells Abraham to impregnate her female slave Hagar. So he rapes her--well, OK to be fair it wasn't rape since they owned her--and then when she gets upset about being pregnant she runs away. Fortunately for our traditional family unit, the Angel of the Lord appears to Hagar and tells her to go back to her master and submit. And so together they have little Ishmael. And so you see, clearly the Eternal Word of God has never changed.... It's always been one man, one woman... LOL
To anyone so concerned about whether other people are doing things unnatural, I would encourage you to worry about yourself. You will be much happier. Put on your reading glasses, after driving your car home, and pop that frozen dinner into the microwave oven, before you turn on your television... Yes you are certainly not doing anything unnatural yourself, you are just as God intended, no aberrations from nature there. LOL
Judging by the likes of Kim Kardashian, Britney Spears, and the divorce rate in general, I think it's safe to say heterosexuality does not inherently imply or guarantee the sanctity of anything.
Life is too short to wage a war against people who just want to enjoy the same Liberty we all do. Lighten up and worry about your own morality. That is the only morality you are legally permitted to control. Not mine, nor my wife's, nor my neighbor's, nor the two gay guys who love each other enough to seal it with the old ball and chain. Mind your own business. It's none of the government's business to tell anyone who they can or cannot marry and we should not have any laws recognizing any form of personal, private romantic union between two people or granting any special rights or privileges as a result of that contract. That is Ron Paul's position on gay marriage too, if I'm not mistaken. It's called Liberty. If you don't like it, then you do not understand the concept of Liberty to begin with and frankly I don't know what you're doing here supporting Ron Paul.