The California Supreme Court said Thursday that supporters of Proposition 8 should be able to pursue their case seeking to uphold the state’s ban on same-sex marriage.

The decision sets the stage for a showdown in the Ninth Circuit Court of Appeals, and perhaps the Supreme Court.

The case had been stalled as the federal Court of Appeals weighed the procedural question of whether the backers of Proposition 8 had “standing” to actually bring and appeal. They are seeking to overturn Judge Vaughn Walker’s decision in August, 2010 that declared that the initiative was unconstitutional. Rather than rule immediately on their own, the three-judge appellate panel asked the state Supreme Court to weigh in.

The American Foundation for Equal Rights, a group of political and entertainment activists who are financing the case for same-sex marriage rights, had argued that the supporters of Prop 8 did not have standing. Nevertheless, org sent out a tweet shortly after the decision was announcing saying, “CA court says forces have standing, paves way for 9th Circuit. Our federal lawsuit for is back on the fast track!”

“In a postelection challenge to a voter-approved initiative measure, the official proponents of the initiative are authorized under California law to appear and assert the state‘s interest in the initiative‘s validity and to appeal a judgment invalidating the measure when the public officials who ordinarily defend the measure or appeal such a judgment decline to do so,” the state high court said in a unanimous opinion.

Then Gov. Arnold Schwarzenegger and then-Attorney General Jerry Brown declined to defend Proposition 8, and the state high court said that preventing supporters from defending the initiative would in effect be giving the two elected officials a veto power over an initiative passed by the voters.

The full decision is here.

Update with some reaction: Brian Raum, senior counsel for the Alliance Defense Fund, said in a statement, “The court was clearly right to conclude that the California marriage amendment should not go undefended just because state officials have refused to defend it. Because the people of California have a right to be defended, Proposition 8’s official proponents will be allowed to continue defending the marriage amendment. Otherwise, state officials would have succeeded in indirectly invalidating a measure that they had no power to strike down directly.”

Kate Kendell, federal exec director of the National Center for Lesbian Rights, said, “We disagree profoundly with the California Supreme Court’s holding that a handful of unelected initiative sponsors have the power to represent the interests of the entire public and to override the decisions of the state’s elected executive officers. Nonetheless, we are relieved that the case is once again moving forward and the Ninth Circuit will now address whether the initiative proponents can continue this appeal and, if so, whether Prop 8 is constitutional.”

Chad Griffin, president of the American Foundation for Equal Rights, put a positive spin on the ruling, even though their legal team argused that Prop 8 supporters did not have standing. He said in a statement, “The Ninth Circuit is the largest appeals court in the nation, stretching the entire west coast and as far east as Montana and Arizona. This is an essential and critical step to bring our case before the U.S. Supreme Court and achieve our ultimate goal: full federal marriage equality.”