(San Francisco, California) Supreme courts this year will rule on cases involving same-sex marriage in Iowa and California.

The Iowa case involves the constitutionality of limiting marriage to opposite-sex couples, while the one in California centers around Proposition 8, the voter-approved amendment to the state constitution that bars same-sex marriage.

In May, the California Supreme Court ruled that the state could not prevent same-sex couples from marrying. Thousands of gay and lesbian couples tied the knot, but opponents of same-sex marriage collected enough signatures for a ballot initiative to place the issue on the ballot.

In November the measure, known as Proposition 8, was approved by a slim majority of voters. Following the election, three challenges to the vote were filed by gay rights groups.

All three cases claim the measure abridges the civil rights of a vulnerable minority group. They argue that voters alone did not have the authority to enact such a significant constitutional change.

The justices said in addition to hearing arguments on the validity of the vote they want to address what effect, if any, a ruling upholding the amendment would have on the estimated 18,000 same-sex marriages that were sanctioned in California before Election Day.

In a surprise move, California Attorney General Jerry Brown told the Court in a brief that it should invalidate Proposition 8, the voter approved amendment to the state constitution that bans same-sex marriage.

It was widely expected that Brown would defend Prop 8.

In its brief to the court, Brown’s office said the measure should be invalidated because it deprives people of the right to marry—an aspect of liberty that the Supreme Court has concluded is guaranteed by the California Constitution.

Supporters of Prop 8 have hired attorney Ken Starr, who led the inquiry into President Bill Clinton’s affair with Monica L. Lewinsky. They argue that the court should uphold Prop 8 and invalidate the 18,000 marriages as well.

In papers submitted to the state Supreme Court, Starr argues that Brown had “invented an entirely new theory” by asking the justices to trump the electorate, which approved Proposition 8 to amend the state Constitution to limit marriage to a man and a woman.

“We will not mince words. The attorney general is inviting this court to declare a constitutional revolution,” the brief reads.

Lawyers for San Francisco and five other counties, as well as for gay couples who married during the four-month window, asked the court Monday to let stand the existing marriages even if it upholds Proposition 8.

They argued that nothing in the language of Proposition 8, nor the ballot arguments submitted by Protect Marriage, made it clear the gay marriage ban was designed to apply retroactively.

The court is expected to hear oral arguments in March. A decision is not likely for several months.

The Iowa Supreme Court heard arguments last month in a challenge to the state ban on same-sex marriage.

In 2007, Polk County Judge Robert Hanson struck down the state Defense of Marriage law, declaring it to be unconstitutional. Later the same day, Hanson stayed the ruling pending an appeal.

Arguing before the high court last month, Assistant Polk County Attorney Roger Kuhle told the justices that Hanson had overstepped his authority.

Kuhle also said that state support of same-sex marriage would damage traditional marriage, arguing that it would indicate to future generations that marriage is no longer about procreation.

Lambda Legal attorney Camilla Taylor, representing the six couples who are challenging the ban on gay marriage, told the court that the law violates Iowa’s constitution.

Taylor said that the constitution protects gay people’s rights to due process and equal protection.

The court is expected to issue its decision later this year.