Here is an excerpt from the Prop 8 proponents’ argument on their standing to appeal:
Proponents have standing to appeal the district court’s judgment because they have “authority under state law,” Karcher v. May, 484 U.S. 72, 82 (1987), to defend the constitutionality of an initiative they have successfully sponsored “as agents of the people of [California] . . . in lieu of public officials” who refuse to do so, Arizonans for Official English v. Arizona, 520 U.S. 43, 65 (1997). In Karcher, the Supreme Court held that the President of the New Jersey Senate and the Speaker of the New Jersey General Assembly had standing to defend the constitutionality of a state statute when “neither the Attorney General nor the named defendants would defend the statute,” because New Jersey law authorized them to do so. In particular, in other cases the “New Jersey Supreme Court ha[d] granted applications of the Speaker of the General Assembly and the President of the Senate to intervene as parties-respondent on behalf of the legislature in defense of a legislative enactment.”
Here also, the California Supreme Court has granted the application of initiative proponents to defend initiatives they have sponsored but the State Attorney General and other public officials refuse to defend—indeed it has done so with respect to these Proponents and Proposition 8. California law thus allows proponents to defend initiatives they have sponsored when government officials “might not do so with vigor” in order “to guard the people’s right to exercise initiative power, a right that must be jealously defended by the courts.” Building Indus. Ass’n v. City of Camarillo (Cal. 1986). Thus, Proponents may directly assert the State’s interest in defending the constitutionality of its laws, an interest that is indisputably sufficient to confer appellate standing. See, e.g., Maine v. Taylor, 477 U.S. 131, 136-37 (1986); Diamond v. Charles, 476 U.S. 54, 62 (1986).
California law thus distinguishes this case from Arizonans for Official English v. Arizona, 520 U.S. 43 (1997). In that case, the Ninth Circuit held that proponents of an Arizona initiative had standing to appeal a decision striking down the measure. Id. at 58. In dicta, the Supreme Court expressed “grave doubts” about proponents’ standing. Id. at 66; see also id. (“we need not definitively resolve the issue”). Citing Karcher, the Court acknowledged that it had “recognized that state legislators have standing to contest a decision holding a state statute unconstitutional if state law authorizes legislators to represent the State’s interests,” but explained that it was “aware of no Arizona law appointing initiative sponsors as agents of the people of Arizona to defend, in lieu of public officials, the constitutionality of initiatives made law of the State.” Id. at 65. Here, by contrast, settled principles of California law, including but not limited to the very same type of legal authority relied upon by Karcher—a State Supreme Court decision permitting intervention—establishes Proponents’ authority “as agents of the people of Arizona to defend, in lieu of public officials,” the constitutionality of Proposition 8.