Discuss as:

Federal appeals court won't revisit California's Prop 8; gay marriage ban likely headed to US Supreme Court

Justin Sullivan / Getty Images

Same-sex couple Frank Capley-Alfano, left, and Joe Capley-Alfano kiss as they celebrate outside of San Francisco City Hall on Feb. 7 after a three-judge panel of the 9th U.S. Circuit Court of Appeals ruled that Proposition 8 measure violates the civil rights of gay men and lesbians.

Updated at 3:11 p.m. ET: A federal appeals court said Tuesday it will not rehear arguments on California's Proposition 8, meaning the final word on the constitutionality of the state’s ban on same-sex marriage will likely come from the U.S. Supreme Court.

A three-judge panel of the 9th U.S. Circuit Court of Appeals ruled 2-1 in February that the ban discriminated against gays and lesbians and served no purpose other than to “lessen the status and human dignity of gays and lesbians.” It rejected the key argument by ban supporters that Prop 8 furthered "responsible procreation."

Prop 8 backers appealed the ruling to the full 9th Circuit, which on Tuesday declined to review it with a larger panel of 11 judges. That clears the way for Prop 8 backers to appeal to the U.S. Supreme Court. They have 90 days to do so.

Read the 9th Circuit Court of Appeals decision

Frank Schubert, political director for the National Organization for Marriage, a key backer and principal funder of Prop 8, said that's where the legal showdown will ultimately be resolved.

“We’re very, very confident in our position on Prop 8 that it is a properly enacted constitutional amendment well within the rights of the people of California to enact, and we are looking forward to that issue going to the U.S. Supreme Court because we are confident that we’ll win it there,” he told reporters on a conference call before the appeals court announcement. “The sooner it can get there the better as far as we’re concerned.”

An attorney for the ban supporters said that his team was preparing for the next round.

"Perhaps the most positive news from today's decision is that the court has stayed the decision up to and including the time that the United States Supreme Court finally decides this case," Andrew Pugno said in a brief statement. "We will promptly file our appeal to the nation's highest court and look forward to a positive outcome on behalf of the millions of Californians who believe in traditional marriage."

Opponents of Prop 8 lauded the refusal to rehear the case.

“Two federal courts in this case have affirmed what we know to be true — that Proposition 8 seriously infringes on the guarantee of equal protection and serves no legitimate state interest,” said Equality California board member David Codell, who provides pro bono legal representation to Equality California on marriage-related issues. “We agree with the majority of the judges of the 9th Circuit that there was no need to rehear this case because the decision to strike down Proposition 8 rested on solid constitutional principles.”

Prop 8 is one of a number of cases involving gay marriage winding through federal courts. Federal judges in Massachusetts and California have in recent weeks declared the Defense of Marriage Act, or DOMA, the federal law that defines marriage as the legal union of one man and one woman, unconstitutional.

Appeals court: Denying federal benefits to same-sex couples is unconstitutional

Six states and the District of Columbia allow same-sex marriage, while 31 states have constitutional amendments that effectively ban gay marriage (this tally does not include California). Maryland and Washington have same-sex marriage statutes passed earlier this year that have yet to take effect and will likely be challenged by ballot referendums in November.

The Defense of Marriage Act, which denies federal benefits to same-sex couples, was declared unconstitutional Thursday. NBC's Matt Lauer reports.

Nationwide, a Gallup poll released in May revealed that 50 percent of Americans say same-sex marriage should be legal, compared with 48 percent opposed. Support for gay marriage fell slightly in that poll from a record high of 53 percent in 2011, the first time a majority of Americans favored gay marriage.

President Barack Obama announced in May that he supported same-sex marriage, becoming the first American president to do so.

The U.S. Supreme Court would set national precedent if it decided to take the case. Appeals courts have so far declined to rule broadly on whether marriage is a fundamental human right for same-sex couples as well as heterosexuals.

The recent federal appeals court ruling in Boston focuses on whether the federal government should follow states' definitions of marriage when determining federal benefits such as Social Security survivor benefits. A federal judge in Oakland struck down portions of DOMA  that have prevented the California Public Employees' Retirement System from extending the insurance to gay spouses and domestic partners. And the three-judge appeals panel ruling in California in February limited itself to Prop 8.

California voters in 2008 passed Proposition 8 by 52.24 percent to 47.76 percent, ending a summer of legal same-sex marriage in the state.

A federal judge struck down Proposition 8 in 2010, although existing same-sex marriages are on hold pending appeals.

More content from msnbc.com and NBC News:

Follow US News on msnbc.com on Twitter and Facebook