From SCOTUSblog:

The judge raised the possibility that the backers of Proposition 8 — the ban approved by the state’s voters in 2008 — may not have a legal right to appeal his decision, since state officials have declined to defend the ban and seem unlikely to pursue their own appeal. The judge declared: “If the state [officials] choose not to appeal, proponents may have difficulty demonstrating Article III standing” — that is, the legal right under the Constituton to be in court.

The judge said he had offered Proposition 8′s backers a chance to spell out a harm that they would directly suffer if their measure were struck down, and the only reply was that they were interested in defending the measure. They failed, he said, “to articulate even one specific harm they may suffer as a consequence” of an order barring enforcement of the marriage ban.

The judge relied quite heavily upon a 1997 decision by the Supreme Court — Arizonans for Official English v. Arizona. That decision involved a 1988 ballot initiative in Arizona, declaring that English was to be the state’s official language. In that decision (written for a a unanimous Court by Justice Ruth Bader Ginsburg), Judge Walker noted, the Justices expressed “grave doubts” whether those who propose a ballot measure have standing separate from state officials to defend the measure’s constitutionality. (NOTE: While the Court expressed those doubts, it ultimately did not resolve whether ballot measure proponents may appeal to defend a measure when the state does not; the case was dismissed as moot, leaving that issue and others unsettled.)

The judge summed up on this point: “As it appears at least doubtful that proponents will be able to proceed with their appeal without a state defendant, it remains unclear whether the courts of appeals will be able to reach the merits of proponents’ appeal. In light of those concerns, proponents may have little choice but to attempt to convince either the Governor or the Attorney General to file an appeal to ensure appellate jurisdiction.”