Proposition 8 (or the California Marriage Protection Act) was a ballot proposition and constitutional amendment passed in the November 2008, state elections. The measure added a new provision, Section 7.5 of the Declaration of Rights, to the California Constitution, which provides that "only marriage between a man and a woman is valid or recognized in California."  

The campaigns for and against Proposition 8 raised $39.9 million and $43.3 million, respectively, becoming the highest-funded campaign on any state ballot that day and surpassing every campaign in the country in spending except the presidential contest. After the elections, demonstrations and protests occurred across the state and nation. Same-sex couples and government entities filed numerous lawsuits with the California Supreme Court challenging the proposition's validity and effect on previously administered same-sex marriages. In the Strauss v. Horton case, the court upheld Proposition 8, but allowed existing same-sex marriages to stand (under the Grandfather clause principle). The ruling was overturned by a lawsuit in federal courts on August 4, 2010. The decision will likely be appealed.