I have now read the whole opinion [see Glenn Greenwald or Balkinization links for a .pdf file hook-up], including the concurrence and dissents, so will add a few remarks.
The majority focuses on the use of "marriage" over "domestic partnership," the terms having difference symbolic effect, which can lead to negative concrete effects. IOW, one is given more respect than the other, with the added problem that mostly (the exception being various senior citizens, for some reason) only same sex couples have the right to have the latter. This in effect outs them when they wish to obtain the rights supplied. The similarity of the two institutions was also referenced by the more sympathetic dissent* -- I'm for it as policy, but sorry, the California Constitution does not demand it and we should not say it does over popular will (e.g., the anti-same sex initiative) -- but it is a bit of a stretch. Not the symbolic effect should be ignored.
Putting aside federal benefits -- which is denied via the Orwellian "Defense of Marriage Act" -- that California cannot do much about, there are around eight differences. Some of them are fairly technical, some minor. But, you need to live together in domestic partnerships, which can very well be troublesome for two career professionals sorts, especially in California ... which much have many couples who live apart much of the time. Not for "marriage." You have to be eighteen to get a domestic partnership. Not so for "marriage." There is a way to keep a marriage license private in some cases. Not so here. You have to get a court order to dissolve a marriage; not so for a domestic partnership. These are real differences, especially the last one, which truly affects the strength of the institution, if negatively.
Domestic partnerships did have a nearly all of the myriad of benefits of marriage, so the majority had a point. And, it might have wrote that for effect -- underlining that even if all the benefits were involved, nomenclature alone can be an issue. Ok. But, they dismissed the claim of gender discrimination rather cavalierly. First, it noted that the law banning interracial marriages in Loving selectively burdened blacks -- races could marry as a whole, just not with a different race that is white. But, the law would have been illegitimate even if the burden was more equitable. Also, the law clearly was racist in intent. Better point there, but even if it was only racist in effect (which the Court seems to be saying in this case), which admittedly is tricky to imagine, it also would have be illegitimate. Right?
Also, the majority in effect noted that gender and sexual orientation was traditionally treated differently, including in state civil rights laws. A case that does a great deal to override tradition suddenly finds it a bit useful. And, there was not intent to discriminate here, including by stereotypical gender roles like stay at home moms. But, the institution of marriage in California clearly had stereotypical gender/sex roles in mind. Marriage was deemed something that only a man and a woman could partake in, from the days of Adam uniting with Eve. Setting forth certain sex and gender roles that clearly affects anti-homosexual animus. And, intent clearly is involved. The fact the argument takes a bit more effort or that it is done as if it is perfectly "natural" and not discriminatory at all (marriage is just naturally man/woman) really does not change this fact.
Not that, some noises aside, no one thinks same sex couples cannot "marry" ... many private and/or religious ceremonies defines it just that way. And, a few cases could be suggested that the idea has been around for some time, including some transgender unions in Native American cultures. Likewise, the institution changed greatly over time, including such things as the roles of each spouse, what institution performs the ceremony, who can marry and so forth. To belabor the point, these are great changes, overall more complete than changing the sex of the participants.**
One last thing. The dissents, even the more sympathetic one, rejected applying strict scrutiny to same sex couples. I am not sure why the latter -- who up-front supported same sex marriage as policy -- did not offer even intermediate review. Anyway, the explanations were a bit lame. The federal courts did not. Well, California recognizes many rights, including strict scrutiny for gender, even though the feds do not. Homosexuals have political power ... when race was first deemed suspect, racial minorities did not have comparable power. But, if the characteristic is immutable, particularly personal, not a legitimate classification (cf. vision), traditionally was discriminated against (and still is -- see federal policy), this should not really matter. As to it being novel, so was applying racial equality to marriage in the 1940s. It has to start somewhere.
Admittedly, when the Massachusetts marriage case was pending, I thought domestic partnerships was a valid middle ground. But, that state did not have them yet, unlike California (or New York as a whole, one might add). The legislature and governor supports same sex marriage. And, easy for me to say that half-way is good for now. Still, given it was not necessary for the decision, it might have been useful to not skip to strict scrutiny. OTOH, marriage seems the last bastion (Florida might disallow adoptions across the board, but it is an outlier) of anti-homosexual bias for some. So, perhaps -- Massachusetts aside -- a bit of heavy lifting was necessary. Still, some middle ground just might get another vote, even if not for marriage in particular.
Anyway, the opinion was good reading. And, if even a fairly Catholic country like Spain can support same sex marriage legislatively, perhaps we can handle it. But, then, we are much more Puritan in some ways then Europeans, huh?
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* The dissents thought it troublesome that the majority allegedly made the legislature's allowance of domestic partnerships come back to bite them by using it to imply same sex couples was accepted by society overall. The majority denied they were really doing this -- even without domestic partnerships, the majority would have decided the same way. OTOH, I think it surely helped their case in some respects.
** The more harsh dissent -- bowing to the need of the courts to override popular will when necessary but whining (we disagree, so we will vent -- I don't know why this is considered proper judicial technique) about "judicial fiat" now -- also raised the incest and polygamy card, though saying it obviously was not comparing the two on the same level. But, what is "incest?" In biblical days, there was various non-blood relation incest taboos, which carry on to the present in various states as to step-siblings. Many states allow even first cousins to marry.
No matter ... the reason the courts will not suddenly allow brother/sister type incest is because society as a whole does not legitimize it on the same level as same sex conduct. This is not to say various imaginative scenarios are impossible -- what if an influx of members of a polygamous culture comes in, perhaps as refugees or whatever? Or, if we really want to go out there, some sort of incestuous alien culture or something? There also must be some cultures that recognize first cousin unions that might come in too.
An old case after all is around involving a religious uncle/niece marriage that a state recognized.