On November 5, 2008, attorneys for the American Civil Liberties Union (ACLU), Lamda Legal, and the National Center for Lesbian Rights filed a writ of petition with the California Supreme Court in an attempt to invalidate Proposition 8. The controversial amendment to the California constitution limits marriage under state law to heterosexual couples and was approved by approximately 52 percent of voters in November 2008. The lawsuit was filed on behalf of Equality California and six same-sex couples who asked the court for a stay of enforcement until litigation challenging the law was resolved. On August 4, 2010, the US District Court for the Northern District of California ruled that Proposition 8's ban on same-sex marriage violated the US Constitution. The governor's office consequently refused to defend the measure and the California Supreme Court has yet to rule on allowing advocacy groups to assume that legal burden.