The SCOTUS decisions on Gay Marriage came to a result that I ultimately agree with but at least in the California decision (on Prop 8) their method of coming to the decision was wrong on many counts. Marriage has traditionally been a state policy issue. Indeed, numerous states have expressed support and opposition to gay marriage. The decision declaring that Congress over-stepped on DOMA is consistent with a strong federal union.
In the Windsor decision they rightly argue that the two plaintiffs from New York were denied equal protection by DOMA. But in California, the voters of the state expressed an opinion on California law not once but twice. The first time they adopted an amendment it was done with a substantial percentage. In the Prop 8 (Hollingsworth) decision the margin was much more narrow.
The political establishment declined to exercise their constitutional responsibility and so the supporters of Proposition 8 took up the cause of defense. The court threw the challenge of the decision of the 9th circuit out by arguing that the plaintiffs did not have "standing" to pursue the issue. But when your elected officials decline to carry out their Constitutional duties the voters who supported Proposition 8 (I did not) are left without a voice. Justice Roberts ignored that question in his majority opinion.
Roberts' arguments sound a lot like the discredited notion of nullification where some states have claimed in the past an ability to nullify some federal enactments that they do not agree with. Only in this case, the nullification is to destroy a key principle of voter passed initiatives - the supremacy of the people over the officials that we have temporarily chosen to work for us.
What might have happened if the court had upheld the right of the people to express their opinion on this matter beyond the ballot box? The structure that is inherent in the initiative is the underlying ability of the people to intervene when their elected officials chose not to. The initiative process is the supremacy of the people has been vanquished to the whims of currently elected officials. Recent polling indicates that if gay marriage would be on a ballot anytime in the future California voters would contradict their earlier judgments.
Those upholding the opinions expressed above, i.e. the ability of voters to protect their supremacy, included an odd mix that included Kennedy and Sotomayor as well as Alito and Thomas. Affirming a popular position while denigrating a more substantive principle is not very judicious.