The packed courtroom audience included actor and director Rob Reiner, as well as other spectators who spent as many as four nights waiting in line, sometimes in rain and snow, to secure a seat for the historic session. Also in attendance was Roberts' cousin, Jean Podrasky, who told the Los Angeles Times this week that she is gay and supports same-sex marriage.
Outside the court, thousands of other people demonstrated on both sides of the issue. Gay marriage supporters cheered a man in a pink fishnet leotard and a rainbow skirt who danced in front of people holding signs that read "Same Sex Marriage Dooms Nation" and "Death Penalty For Fags."
California voters approved Proposition 8 in 2008. The ballot initiative reversed a decision by the California Supreme Court, which five months earlier had said the state constitution guaranteed the right to gay marriage.
Gay marriage is on hold in California while the litigation plays out. More than 18,000 same-sex couples were married in the state before the ballot initiative passed.
In challenging the law, former Republican Solicitor General Theodore Olson joined forces with David Boies, his opponent from the Bush v. Gore case, which resolved the 2000 presidential election deadlock. The pair, representing two same- sex couples, set out to win a Supreme Court ruling establishing gay marriage as a constitutional right.
At the appeals court level, they instead won a narrower ruling with limited applicability beyond California's borders. The San Francisco-based 9th U.S. Circuit Court of Appeals said Proposition 8 violated the constitutional guarantee of equal protection by stripping same-sex couples of a right they once had -- and that heterosexual couples would continue to possess.
Supporters of the law are led by Dennis Hollingsworth, a former California state senator.
Their lawyer, Charles Cooper, said Tuesday that states should be allowed to work through the "agonizingly difficult issue."