In oral arguments in San Francisco, the plaintiffs argued that the state constitution protects the right of same-sex couples to formally marry based on the court's 1948 decision striking down a ban on marriage between people of different races.

The San Francisco Chronicle said the plaintiffs said the decision clearly stated that the "right to join in marriage with the person of one's choice" had been recognized by the court.

The state maintained, however, that banning same-sex marriage actually strengthens state laws on domestic partnerships.

California Deputy Attorney General Christopher Krueger also told the justices that interracial couples didn't have such partnerships to fall back on in the 1940s. He added that the law was implemented purely for racial-superiority purposes and that domestic partnerships couldn't be considered "exclusionary" since they contained all of the legal rights inherent in marriage.

The justices have 90 days to issue a ruling in the case.