On August 4th, a disrict court judge Vaughn Walker struck down California's ban on gay marriages. This isn't the first time the courts have upheld a right to marry a person of your own sex, but it is the first time it's been done by claiming that a right to same-sex marriage is protected by the US federal Constitution; previous decisions have all been based on the rights enumerated in state constitutions.
This is kind of a big deal, to put it mildly. If this interpretation is upheld by the Supreme Court, it would suddenly strike down all bans on gay marriage nationwide.
I'm very, very pleased with the effect of the decision, but whether the ruling is actually legally correct... That's a complicated question.
The oft-ignored Ninth Amendment makes it clear that the Bill of Rights isn't a comprehensive list of every right protected by the Constitution; all rights 18th Century Americans believed themselves to have are Constitutionally protected against federal interference unless specifically modified by the Constitution. And the battered Fourteenth Amendment extends that protection to state interference, too. So if Revolutionary-era Americans thought they had a God-given-dammit right to marry (and they certainly seem to have), then the states today must respect that right.
The problem lies in determining what restrictions early Americans recognized on a given right, and how those do or don't apply to modern rights. In the case of Perry, early Americans would most definitely have understood a right to marry as not extending to the right to marry a person of your own sex. But how relevant is that to modern Constitutional interpretation? I see three important factors:
First, early Americans didn't always fully live up to letter of the Constitution. The Second Amendment explicitly extends a right to arms to "the people", but Americans of the time freely denied that right whenever black people wanted to exercise it. And this is obviously only one tiny, tiny example: huge expanses of liberties were merrily ignored when the person trying to exercise the right had the wrong skin color or genitalia. The legitimate expansion of freedom in the US over the centuries has revolved primarily around extending existing rights to people who'd previously been denied them. With this understanding, I think a traditional denial of marriage rights to "gay" Americans (understanding the difficulty of applying modern concepts of sexual identity to past communities) may be entirely irrelevant to the modern extent of the right. If a thing is a right, it's a right for everybody, and no precedent of past discrimination will make it otherwise.
Second, our understanding of Constitutional rights must acknowledge that they protect modern equivalents of 18th Century protected activity. Freedom of the press isn't restricted merely to hand operated movable type presses, nor the right to arms to muzzleloading muskets, so it doesn't make much sense to insist that a right to marriage only protects the kind of marriage widely practiced in 1788. If it did, the Constitution would only protect a right to a marriage stuctured under the then-standard model of coverture. We as a culture have accepted "redefining marriage" to accept a modern understanding that wives are not property and "races" can mix; if two men or two women want to exercise a right in yet another previously unconventional way, precedent shows that we should take a broad view of fundamental rights in a changing world.
Finally, given the above, the disagreement really reduces to two competing ideas of what the modern "right to marriage" means. Is it a right to do as you please with regard to marriage, an expansive right whose scope just hasn't been fully respected yet; or is it a narrow right that a man and a woman have to marry for the purposes of promoting a traditional* family model? Ironically, if you take the traditional American "conservative" view of rights (that a right to X protects the individual against government intrusion into his decisions about X, and generally supersedes collective-good arguments), then gay marriage--and poly marriage, for that matter--certainly seems to be a right the states can't interfere with. On the other hand, if you take the traditional American "liberal" view of rights (that a right to X is a socially-constructed quantity, applying to an individual or to a collective, with variable meaning that's tuned by government for the greatest benefit to the citizen and the community), then state or federal bans on gay marriage may be ill conceived or counterproductive, but they certainly aren't unconstitutional. I think the former is the correct interpretation, Constitutionally speaking, so I agree with Judge Walker: the Constitution seems to compel both state and federal govenments to stay the hell out of the individual's decision to marry any given person or people he pleases**.
In general, I'm very wary of reading rights into the Constitution. As much as I support a right to make one's own decision about whether to get an abortion, reading that right into the Constitution sets an extremely dangerous precedent. Constitutional rights exist to protect fundamental rights from the changing tides of public opinion, and Roe-style free reinterpretation for the sake of advancing a social policy--however solid the policy--weakens that protection. But I don't think the same problem applies in the case of Perry, any more that it does in extending 1A protections to blog posts, 2A protections to AR-15s, and 4A protections to wiretapping. Essentially, it's a matter of extending a fundamental right to people who were previously denied that right. This isn't the first time we've been down this road, and it won't be the last.
[* - Let's not get into that right now. You know what I mean.]
[** - Contrary to the standard line, this doesn't mean Warren Jeffs' behavior is Constitutionally protected. There are fundamental differences in the decisionmaking capacity of children versus adults, so age-of-consent laws are defensible as a fundamentally different question from adults' right to marry as they see fit. Slippery slope arguments can be valuable, but this one is invalid.]