The California Supreme Court granted (cert? discretionary review? not sure how the state's system works) review of three lawsuits challenging the gay marriage ban.
I know nothing more about California law than what I've read in conjunction with this issue, but it seems like the lawsuits have a decent legal argument. Essentially, they're arguing that this is not just an amendment to the constitution, but a change in a legal right that the constitution guaranteed. That's a subtle distinction, but an important one: ballot initiatives can accomplish the former, but not the latter.
The problem is this: even if it's a valid and sound legal argument, it will still be looked at as an attempt to thwart the "will of the people." Of course, that's pure crap -- Prop 8 was passed with 51% of the vote, and maybe 50% of the eligible voters voted in the election. So it's the will of a quarter of the people.
That attack is also crap in another way: the courts are supposed to protect vulnerable minorities from majoritarian excesses. If the 25% of the California population that's still bigoted can use a loophole to change the legal status of citizens, that's a problem. And the courts are supposed to prevent that from happening.
Imagine if this were the 1960s, and Prop 8 forbade interracial marriage. Some of the same people who are against gay marriage now were against (and probably still are, though under the radar) interracial marriage.
Of course, it took a court case to put an end to the de jure prohibition against interracial marriage (Loving v. Virginia). It will probably take another court case to end the modern version of that hatred.
The current SCOTUS isn't likely to look favorably on such a case, but luckily for the Prop 8 challenge, it won't get the chance to rule: the Prop 8 lawsuits are purely a matter of state law, and SCOTUS has no jurisdiction there (unless the challenge is that state law violates the federal constitution, but that argument isn't being made).
California's Supreme Court to Take Up Gay-Marriage Ban - WSJ.com