WASHINGTON (Reuters) - America's top court takes up the delicate and divisive issue of gay marriage on Tuesday when the nine Supreme Court justices consider the legality of a California ballot initiative that limits marriage to opposite-sex couples.
Tuesday will be the first of two days of oral arguments on the issue. On Wednesday, the court will consider the 1996 federal Defense of Marriage Act (DOMA), which limits the definition of marriage to opposite-sex couples.
Rulings in both cases are expected by the end of June.
In what is scheduled to be about three hours of deliberations with lawyers over the two days, the justices will have their say on what gay activists see as a key civil rights issue reminiscent of famous Supreme Court cases of the past, including Loving v. Virginia, a 1967 case in which the court invalidated bans on interracial marriage.
The cases come before the high court at a time when more states have legalised gay marriage. Last year three more - Maryland, Maine and Washington - did so, bringing the total to nine plus the District of Columbia.
"Never before in our history has a major civil rights issue landed on the doorstep of the Supreme Court with this wave of public support," said Mr Theodore Boutrous, a lawyer for opponents of the California intitiative, which is known as Proposition 8.
Strong opposition to gay marriage still exists, however, both among Republicans in Congress and in many states across the nation. A total of 30 states, including California, have constitutional amendments that ban gay marriage. Nine states, including California, recognise civil unions or domestic partnerships among same-sex couples.
Advocates for both sides plan to demonstrate outside the multi-columned Washington courthouse. Those who plan to attend include Chief Justice John Roberts' cousin Jean Podrasky, a lesbian from California who would like to marry her partner.
"There's no fundamental right to same sex marriage in the US Constitution," said Mr Austin Nimocks, a member of the legal team arguing in support of the California law.
Some legal experts think that with the issue unsettled in the states, a majority of the justices might not be inclined to make any sweeping pronouncements on the issue as the democratic process plays out.
There are various ways in which they could do that as the Proposition 8 case presents the justices with multiple options.
The justices could proclaim that gay marriage bans are constitutionally unsound. They could uphold Proposition 8 as a law with a legitimate purpose that was approved by a majority of voters in California. They could also plot a middle path by striking down the law without making any broad pronouncements about whether gay marriage bans in other states that have them should be struck down.
Another way the court could rule might be viewed as an anticlimax of sorts: The justices could simply decide that it cannot rule on the merits because of the procedural complexities that brought the case to the high court.
The state of California declined to support Proposition 8 when the plaintiffs filed suit in 2009 in a federal district court in San Francisco, meaning there was no party defending the law until its proponents entered the case. The federal judge struck the law down, a ruling that was upheld by the San Francisco-based 9th US Circuit Court of Appeals.
A Supreme Court decision concluding that the law's backers do not have legal standing to defend the law would wipe out the appeals court decision, but leave the district court decision that struck down Proposition 8 on the books.
The way the justices rule could depend in large part on the likely swing voter, Justice Anthony Kennedy. Although a conservative appointed by President Ronald Reagan, judge Kennedy has in the past authored two opinions that expanded gay rights.
Lawyers representing two same-sex couples in California who want to marry are hoping the justices will go big and are making the most sweeping arguments.
The counsel for Ms Kris Perry and Ms Sandy Stier and Mr Paul Katami and Mr Jeff Zarrillo will argue that under the US Constitution's equal protection guarantee, there is a fundamental right for people to marry someone of the same sex.
Ms Kris Perry, who has raised four children with her partner, Ms Sandy Stier, was hopeful and optimistic.
"We have been waiting for a long time to get married," she said last week. "We are very excited to have the end in sight."