At the root of the Supreme Court’s consideration of California’s voter-approved gay marriage ban is a question of whether private citizens should be allowed to defend a state law when that state’s officials refuse to do so.

It won’t dominate the headlines like the juicier issues of individual rights and the fundamental purpose of marriage, but it could be the most important question of the day.

The standing issue is being raised because the petitioners (who want California’s ban on same-sex marriage to be upheld) aren’t state officials. Typically, states' attorneys general defend a state law in federal court, but Gov. Jerry Brown and his administration refused to advocate for the 2008 ballot initiative that defined marriage as between a man and a woman. So instead, some of the private citizens who helped the ban succeed took up the case.

If the court decides that the petitioners don’t have the legal standing to defend the law in the first place, they can dismiss the case without making a substantive ruling. But the court’s ruling on the standing question specifically could have long-lasting implications beyond this particular issue. If the court decides that the petitioners do have standing, it would conceivably open the door for private citizens to assert themselves into future cases when the government does not defend an existing law.

During Tuesday’s oral arguments in Washington, D.C., Charlie Cooper, the lawyer representing the petitioners, noted that the California Supreme Court previously ruled that Proposition 8 supporters did have standing to defend the law if Brown’s administration wouldn't. He also argued that unless his clients were granted legal standing, state officials would essentially have veto power to overturn any voter-approved ballot initiative that they didn’t like.

“The initiative process is designed to control those very public officials, to take issues out of their hands,” Cooper said. “If public officials could effectively veto an initiative by refusing to appeal it, then the initiative process would be invalidated.”

The four conservative justices as well as Justice Anthony Kennedy, who's widely considered the most important swing vote on these cases, gave some sympathy to that argument.

“The proponents … must give their official address, they must pay money, they must all act in unison under California law,” Kennedy said. “In that sense, it’s different from saying any other citizen (could defend the law).”

“In a state that has initiative, the whole process would be defeated if the only people who could defend the statute are the elected public officials,” conservative Justice Samuel Alito told attorney Ted Olson, who represented the supporters of same-sex marriage and argued that the opponents don't have standing to defend Proposition 8. “The whole point of the initiative process was to allow the people to circumvent public officials about whom they were suspicious," Alito argued.

Olson and the four liberal justices, though, argued that because same-sex marriage opponents aren't injured or harmed if gay couples are allowed to marry, they don’t have a grievance to bring before the court.

“Could the state just assign to anybody the ability to do this?” Justice Elena Kagan asked Cooper. A few minutes later, Justice Sonia Sotomayor probed further: “These individuals are not elected by the people or appointed by the people. … How does this create an injury to them separate from that of any other taxpayer?”

Cooper countered that preserving the traditional definition of marriage (as between a man and a woman) and defending a voter-approved ballot initiative that his clients were actively involved in passing was enough of a justification for the petitioners to have standing.

There were no clear indications on which way the court will rule on the standing issue. The liberal justices heavily questioned whether the petitioners have legal standing. However, if they decide that the petitioners don't have standing, they hamper their ability to make a broader ruling on gay marriage that would have an impact beyond California. The conservative judges appeared more receptive to the idea of legal standing from the start.

Kennedy, the swing vote, was much more difficult to read. At first, he seemed opposed to the idea that state officials could effectively overturn a ballot initiative by refusing to defend it in court. But toward the end of Tuesday’s arguments, he appeared equally unsettled by the idea of making a substantive ruling on the case and seemed to suggest dismissing the case on standing as a way out.

“The problem with the case is that you’re really asking … for us to go into uncharted waters,” Kennedy said to Olson, referring to same-sex supporters’ argument that any bans on same-sex marriage are unconstitutional. “But you’re doing so in a case where there’s a substantial question on standing. I just wonder if the case was properly granted.”