(CNN) -- A complex legal fight over the constitutionality of same-sex marriage is back on track after California's highest court on Thursday allowed an appeal over a controversial ballot initiative to move ahead in federal court.
At issue is Proposition 8, a voter-approved measure that would recognize marriage only between one man and one woman. A federal judge had earlier struck down the law as a violation of equal protection, prompting an appeal to a higher court.
The sticking point was who would defend "Prop 8" in court, after the state's top officials -- including the governor and attorney general -- refused to do so. A federal appeals court had asked the California Supreme Court to weigh in and decide whether supporters of the law -- called the "official proponents" -- could take the place of state officials.
In its ruling Thursday, the state high court said yes.
"Neither the governor, the attorney general, nor any other executive or legislative official has the authority to veto or invalidate an initiative measure that has been approved by the voters," said the court's majority. "It would exalt form over substance to interpret California law in a manner that would permit these public officials to indirectly achieve such a result by denying the official initiative proponents the authority to step in to assert the state's interest in the validity of the measure or to appeal a lower court judgment invalidating the measure when those public officials decline to assert that interest or to appeal an adverse judgment."
The issue now goes back to the 9th Circuit U.S. Court of Appeals, which ultimately will decide the "standing" -- or legal authority -- question, and whether initiative proponents can defend Prop 8. The state high court ruling is not binding on the federal courts, but is likely to be supported by the 9th Circuit as it renews its consideration of the larger constitutional questions.
Among the measure's biggest defenders is the National Organization for Marriage, the largest contributor to qualifying the measure on the 2008 ballot.
"It has been nothing short of shameful to see Governor Jerry Brown, his predecessor Arnold Schwarzenegger and Attorney General Kamala Harris abdicate their constitutional responsibility to defend Proposition 8 in court," said Brian Brown, the organization's president.
"It is gratifying to know that the over 7 million Californians who supported the initiative will have a vigorous defense of their decision in our federal courts," he added.
State officials traditionally defend ballot measures in court, and the question had never been settled in California over who could step when those officials refused to do so. Gay rights groups had urged Brown and Schwarzenegger not to support Prop 8, which is called the California Marriage Protection Act by supporters.
The 9th Circuit, in a hearing nearly a year ago, indicated it was inclined to toss out Prop 8 if the issues over standing could be settled. Federal District Court Judge Vaughn Walker -- who has since retired -- had also overturned the measure after a two-week trial in 2010, saying gay and lesbian couples were unfairly denied the right to marry. Walker has since acknowledged he has been in a committed same-sex relationship.
Both sides of the dispute acknowledge the issue of same sex-marriage is headed to the U.S. Supreme Court, perhaps within the coming year.
The California Supreme Court ruling is Perry v. Brown (S189476).