As the U.S. Supreme Court considered whether states can ban same-sex marriage Tuesday, the justices appeared torn over whether it’s too soon to make a broad decision on the issue and whether they should even make a ruling at all as the case before them raises serious doubts about who should be able to defend a voter-passed ballot initiative in federal court.

It's the first of two cases related to gay marriage that the court will hear this week. The second case, to be heard Wednesday, challenges the federal Defense of Marriage Act (DOMA), which defines marriage as between a man and a woman under federal law and prohibits the federal government from recognizing same-sex marriages that are legal under state law.

In today's hearing, Chief Justice John Roberts sharply directed each attorney to address whether the petitioners, the supporters of Proposition 8, which banned gay marriage in California, should be allowed to advocate in favor of the law even though they're not state officials. The petitioners argued that they gained legal standing when Gov. Jerry Brown and his administration declined to defend the law. But the law's opponents (supporters of same-sex marriage) argued that their case has no legal standing because they wouldn't be injured if the law were overturned and same-sex couples were allowed to marry.

Should private citizens be allowed to defend state laws in court?

The liberal justices -- Stephen Breyer, Ruth Bader Ginsburg, Elena Kagan and Sonia Sotomayor -- repeatedly challenged Charles Cooper, the lawyer representing the opponents of same-sex marriage, over his client’s standing. Even Justice Roberts, a conservative, questioned the issue of legal standing.

“How does it create injury for [the petitioners]?” Kagan asked. “Or could the state assign to any citizen the rights to defend a judgment of this kind?”

Breyer asserted that they aren’t representatives of the state. "They are really no more than a group of five people who feel really strongly [about the issue.]”

Cooper routinely relied on the California Supreme Court’s previous finding that the petitioners did have standing to defend the case. Conservative Justice Samuel Alito and Anthony Kennedy, who's widely viewed as a swing vote in the case, seemed to concur with the state court's ruling.

Kennedy alluded that not allowing the case to proceed because it doesn't have legal standing would "allow governors and other constitutional officers in different states to thwart the initiative process." 

The question of standing will determine whether the court makes a substantive ruling on the Prop. 8 case at all. But once the arguments moved to the merits of each side’s case, there was again a sharp divide between the justices.

The marriage label

Two issues are inherently intertwined at the heart of the case: What is the purpose of marriage? And: Should the court disregard the popular vote of a state’s residents when the question of same-sex marriage is still so young?

The liberal justices pushed Cooper to explain what makes marriage unique, frequently pointing out that California offers same-sex couples almost all of the same rights as opposite-sex couples, such as adoption.

“Outside of the marriage context, can you think of any other rational basis, reason for a state using sexual orientation as a factor in denying homosexuals benefits?” Sotomayor asked. Cooper countered that the interest in regulating procreation gives the states an active interest in defining marriage as being between a man and a woman. Sotomayor and others challenged Cooper's argument, noting that many opposite-sex couples don't have children.

Roberts, during the arguments of same-sex supporters, turned this perspective around and asked rhetorically if same-sex marriage supporters were mostly interested in a label, considering that they already had many of the same rights as opposite-sex married couples.

Once thought as a potential swing vote, Roberts also seemed to voice support for defining same-sex unions differently than traditional marriage.

"I'm not sure that it's right to view this as excluding a particular group," Roberts said. "When the institution of marriage developed historically, people didn't get around and say let's have this institution, but let's keep out homosexuals. The institution developed to serve purposes that, by their nature, didn't include homosexual couples."

Letting the people decide

Toward each side’s conclusion, the arguments centered around whether now was the right time for the court to make a decision about same-sex marriage when it's such a new institution. On several occasions, Cooper referred to the “agonizing” national debate around the issue and implied that the court should allow the democratic process to play itself out. He also argued that the ramifications of legalizing same-sex marriage nationwide are simply too great of an unknown.

The conservative justices, including Roberts, seemed to sympathize with that argument and repeatedly referred to same-sex marriage as an unsettled issue.

“We do not have the ability to see the future. On a question like [this], of such fundamental importance, why should it not be left for the people?” Alito said. “There isn’t a lot of data about [gay marriage's] effect. It may turn out to be a good thing. It may turn out not to be a good thing, as the supporters of Proposition 8 apparently believe.”

MAP: Which states allow same-sex marriage and civil unions?

Kennedy appeared conflicted. At one point, he referenced the children of same-sex couples in California who might currently be harmed because their parents cannot get married.

“I think there's substance to the point that sociological information is new,” he said. “On the other hand, there is an immediate legal injury -- what could be a legal injury -- and that's the voice of these children. There are some 40,000 children in California, according to the Red Brief, that live with same-sex parents. They want their parents to have full recognition.”

But Kennedy later seemed hesitant about extending same-sex marriage rights nationwide.

“You’re really asking ... us to go into uncharted waters,” he told attorney Ted Olson, who represented the supporters of same-sex marriage. At one point, he questioned whether the Court should rule at all.

"I just wonder if the case was properly granted," Kennedy said. That comment has already led some long-time court watchers, such as SCOTUSblog, to deduce that Kennedy might try to form a coalition to dismiss the Prop. 8 case without a ruling on the merits.

Prop. 8 was passed by California voters in November 2008 in response to a California Supreme Court ruling earlier that year that declared same-sex couples had a right to be married. The subsequent lawsuit was brought by two same-sex couples that then attempted to obtain marriage licenses. The U.S. District Court of Northern California ruled in the couples’ favor and went a step further, declaring that any state law that infringed on same-sex couples’ rights was unconstitutional.

The Ninth Circuit Court of Appeals upheld the district court’s ruling with a narrower decision, deciding that California could not take away same-sex couples’ right to marry after previously granting it to them.

Possible outcomes

The Supreme Court has a few options in how it rules on the Prop. 8 case.

It could decide that the petitioners don't have standing because they wouldn't be harmed if the lower courts’ rulings were upheld. This would likely restore same-sex marriage in California, but effect only California.

The court could also rule along the lines of the circuit court, concluding that a state cannot take away marriage rights after previously granting them, which would again only apply to California.

Or the court could take a broader ruling.

The Obama administration has argued, as a “friend of the court”, in favor of a new interpretation which reasons that states that offer same-sex partnerships almost identical rights to opposite-sex marriages cannot deny them the right to ‘marry’ properly. This would likely apply to the nine states that have legalized same-sex civil unions but not marriage.

Or, in the broadest possible decision, the court could agree with the district court and declare that any state law limiting the rights of same-sex couples is unconstitutional. This would likely overturn laws passed in more than 30 states that ban same-sex marriages.

A ruling will likely come in June, near the end of the Court's current term.

The official transcript appears below.