WASHINGTON - May 26 - Americans United for Separation of Church and State today expressed disappointment with the California Supreme Court ruling upholding Proposition 8, which bans same-sex marriage in the state.

"Marriage is a civil right and should not be subject to majority rule or a religious litmus test," said the Rev. Barry W. Lynn, executive director of Americans United.

"It is a decision at odds with both the Constitution and basic decency," Lynn continued. "History will judge that this was a step backward for religious freedom and civil rights."

After a divisive campaign led largely by conservative religious groups, California voters narrow approved Proposition 8 in November of 2008. The vote had the effect of nullifying a May 2008 ruling by the state high court legalizing same-sex marriage.

Gay-rights groups subsequently challenged the vote in court, arguing that fundamental changes to the California Constitution can be made only through a deliberative process that begins in the legislature, not ballot initiatives.

Americans United, the Anti-Defamation League and 30 other civil rights and civil liberties groups joined the effort, filing a friend-of-the-court brief asserting that a bare majority of voters should not be permitted to remove fundamental rights from a minority group.

"If Proposition 8 can strip fundamental rights from gay and lesbian people by a 52 percent majority, future amendments can strip away fundamental rights from other disfavored groups based on race, national origin, gender or religion," read the brief.

"Today's ruling is unfortunate, but it's not the end of the fight," Lynn said. "I'm confident that Californians will rise up and reject the divisive agenda of the Religious Right."

Americans United is a religious liberty watchdog group based in Washington, D.C. Founded in 1947, the organization educates Americans about the importance of church-state separation in safeguarding religious freedom.