[Ed. note: See als bmaz' analysis of this punt at this link.]
Punting to the California state Supreme Court, the federal Ninth Circuit Court of Appeals panel that heard the appeal last month of Judge Vaughn Walker’s decision has asked this question:
Where under Article II, Section 8 of the California Constitution, or otherwise under California law, the official proponents of an initiative measure possess either a particularized interest in the initiative’s validity or the authority to assert the State’s interest in the initiative’s validity, which would enable them to defend the constitutionality of the initiative upon its adoption or appeal a judgment invalidating the initiative, when the public officials charged with that duty refuse to do so.
There’s lots more to justify asking the question; you can read the ruling here: http://bit.ly/gCvdE6 [pdf]