The California Supreme Court has announced that on Tuesday it will issue its ruling on a challenge to the voter-approved measure that reinstated the state's ban on same-sex marriage.

Three lawsuits have been filed by same-sex couples and local governments, led by San Francisco, seeking to overturn Proposition 8, which 52% of California voters approved in November. If the court upholds the measure, it must also decide how the proposition affects the marriages of about 18,000 same-sex couples who wed before the Nov. 4 election, the San Francisco Chronicle writes

The court will issue its ruling at 10 a.m. PT (1 p.m. ET) and post the opinion here. You can also sign up for an email notification.

Prop. 8 amended the state Constitution to declare that only marriage between a man and a woman is valid or recognized in California. That trumped the court's 4-3 ruling in May 2008 that struck down the state's previous heterosexual-only marriage law. The justices declared the law unconstitutional, saying it violated the rights of gays and lesbians to marry the person of their choice and discriminated on the basis of sexual orientation.

All court filings related to Prop. 8 can be found here.