Today was the first day of a federal trial challenging the constitutionality of California's Proposition 8. Here's a passionate defense of the lawsuit by conservative challenger Ted Olson. Andrew Sullivan (one of my favorite political commentators, a homosexual himself) also comments about it here, and generally keeps up-to-date with interesting stuff on his blog.
Most people, liberal and conservative alike, expect the amendment's challengers to lose and the amendment to stand. The case is most interesting for me fro showing--and I say this with some apprehension--that the Constitution will always be no more progressive than the people reading it. The case hinges a non-traditional interpretation of section 1 of the 14th Amendment, which was written by an immensely progressive (loyal states only) Congress in the immediate aftermath of the Civil War with the intention of preventing Southern states from adopting and enforcing discriminatory laws, especially against the newly freed slaves.
In Constitutional law, the traditional "rights-augmenting" provision of the 14th Amendment is the "equal protection" clause of section 1 (for twisted jurisprudential reasons, explained here, the "privileges and immunities" of the second sentence have been interpreted to apply principally to "port access," rather than, as originally intended by the authors, the rights in the Bill of Rights). One should note that the equal protection clause is meaningless as plainly written. A law that only allows marriage between one man and one woman, or one white man and one white woman, can be equally enforced, or "protected", for homosexuals and heterosexuals, blacks and whites alike. Any law that has discriminating language written into it can easily be enforced equally across the population. The language of the 14th Amendment is interpreted more liberally to bar "discriminatory" laws, and thus it is the basis for most landmark civil rights cases (Brown v Board of Education, Loving v Virginia, etc.).
But since the language is so general, it really can come to mean whatever judges at the time decide. On the one hand, the general language is a reflection of the authors' intention that the Amendment be perpetually interpreted progressively. They could have easily written that states couldn't abridge the civil rights of blacks, but instead they made the language much more sweeping, to apply not just in the moment but to civil rights disputes of the future. Once there is a social consensus in favor of homosexuals' marriage rights, hopefully within the next decade, then I have no doubt that their rights will be forever enshrined in the equal protection clause. For now, judges probably just don't see the discrimination as quite blatant and obvious enough, and they'll come up with plenty of reasons to let the amendment stand.