/ Actor and producer Clint Eastwood is seen in September 2012 in Westwood, Calif.

Clint Eastwood has joined about 130 self-described moderate and conservative Republicans in signing a brief to the Supreme Court arguing against California’s Proposition 8, which bans marriage for same-sex couples.

Former Bush administration officials, including Paul Wolfowitz, deputy secretary of Defense, and Tom Ridge, former Pennsylvania governor and Secretary of Homeland Security, also were among those who signed the brief, which argued that the Constitution prohibits denying same-sex couples access to the legal rights and responsibilities of marriage, according to a copy of the brief released Thursday by the American Foundation for Equal Rights.

Breitbart.com, which first reported that Eastwood had signed the brief, said he was a "long-time Republican with strong libertarian leanings," who had "become increasingly vocal politically." Eastwood's conversation with an empty chair representing President Barack Obama on the final day of the Republican convention briefly became a major topic on the campaign last fall.

The nation’s high court will hear arguments in the case on March 26. Thursday is the last day for briefs to be filed in the case, and officials told NBC's Pete Williams that the Justice Department will urge the court to approve gay marriage in California.

Six other former governors, including Jon Huntsman of Utah and Christine Todd Whitman of New Jersey, and ten former and two current members of Congress signed the brief, which was organized by AFER. Members of the George W. Bush, Mitt Romney and Sen. John McCain presidential campaigns also signed.

In the brief, the group said it was better for children to grow up with married parents, and that legalizing same-sex marriage would ease couples’ access to benefits and rights afforded to heterosexual couples but would pose “no credible threat to religious freedom or to the institution of religious marriage.”

They noted that many of those adding their names did not previously support same-sex marriage. But since a number of states have allowed gays and lesbians to wed, they, "like many Americans, have reexamined the evidence and their own positions and have concluded that there is no legitimate, fact-based reason for denying same-sex couples the same recognition in law that is available to opposite-sex couples."

Rather, they “concluded that marriage is strengthened, not undermined, and its benefits and importance to society as well as the support and stability it gives to children and families promoted, not undercut, by providing access to civil marriage for same-sex couples,” the brief continued.

Some on the list included who have had a change of heart on the issue include Meg Whitman, the Republican candidate for California governor in 2010, and David Frum, a special assistant to Bush from 2001 to 2002.

Once 'inconceivable,' Republican leaders sign pro-gay marriage brief

Numerous briefs have been filed in support of Prop. 8 by 20 states, religious groups, academics and legal scholars, as well as many against by businesses, labor unions, veterans, California plus thirteen states as well as the District of Columbia, and gay rights and religious groups.

National Football League players, Chris Kluwe, a punter for the Minnesota Vikings, and Bredon Ayanbadejo, a linebacker for the Baltimore Ravens, also filed a separate brief in the case that was released Thursday afternoon. The pair has been outspoken supporters of gay rights.

The California Supreme Court said in 2008 that the state had to allow same-sex marriage, and for a short period, some 18,000 same-sex couples wed in the Golden State. But with the passage of Prop. 8 later that same year, gays and lesbians were later prohibited from marrying. Various lower courts said the law was unconstitutional, with the most recent one determining such a fundamental right like marriage, that gays and lesbians had once enjoyed, could not be taken away.

The Supreme Court will also hear arguments in late March on Section 3 of the Defense of Marriage Act, which bars federal recognition of same-sex marriage. The Obama administration has encouraged the justices to strike down Section 3. In its argument, the administration noted that Proposition 8 and similar measures in other states were evidence that anti-gay discrimination remained a major problem.

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