On June 14 the board of Atheists United unanimously passed a resolution in opposition to the California Attorney General's proposed constitutional amendment titled "Limit on Marriage:"

WHEREAS, the California Supreme Court has ruled that "the right to marry is not properly viewed simply as a benefit or privilege that a government may establish or abolish as it sees fit, but rather that the right constitutes a basic civil or human right of all people" (In re Marriage Cases S147999, May 15, 2008, footnote 41),
WHEREAS, a proposed constitutional amendment to limit marriage, will be on the November 4, 2008 General Election Ballot in California stating "Only marriage between a man and a woman is valid or recognized in California,"
WHEREAS, such a limit on the right to marry is based on religious belief, not on the reasonable interests of the state, and therefore is an effrontery to the separation of government from religion,
THEREFORE, Atheists United declares its opposition to this ballot measure and urges other organizations and individuals to oppose the measure and to vote against it.

The board believes that the mission of Atheists United compels us to oppose this amendment because it imposes limitations on atheists and others based on specific religious dogmas. Furthermore, the board believes that taking this stand will reflect well on atheists and on Atheists United. As the resolution states, we "urge other organizations and individuals to oppose the measure." The board hopes to collaborate with other secular organizations and thus further the cause of atheism in this case and potentially in other future cases.

Until 1977, California did not explicitly define marriage as being between a man and a woman, however, court decisions, assumed as much. In 1977 the legislature amended Civil Code to read that marriage is "a personal relation arising out of a civil contract between a man and a woman."
In 2000, voters passed a ballot initiative, Proposition 22, which confirmed this view. However, other laws recognized domestic partnerships and afforded them some of the rights of marriage. A number of developments arose in the wake of Mayor Gavin Newsom's 2004 decision to perform same sex weddings in San Francisco. A number of legal challenges were consolidated for the Supreme Court as "In re Marriage Cases." On May 15, 2008 the California Supreme Court struck down Proposition 22 and all other prohibitions against same-sex marriage as violating the state constitution

At least four different groups have sponsored new ballot initiatives for a constitutional amendment prohibiting same-sex marriages. The one that was approved on June 2 for the November 4 general election was sponsored by ProtectMarriage.com The sponsors wish the amendment to be known as the "California Marriage Protection Act." The intention is, of course, to override the Supreme Court ruling, "In re Marriage Cases"

For further details see
http://en.wikipedia.org/wiki/California_Marriage_Protection_Act