America's debate over same-sex marriage will take center stage in a California courtroom today at a closely watched federal trial that could ultimately become the landmark case that determines whether homosexual Americans have a right to marry.

At issue in the trial starting today in San Francisco is whether the Proposition 8 gay marriage ban approved by California voters in November 2008 is legal.

The presiding judge has agreed to allow video of the trial to be posted on YouTube.com several hours later.

Late Friday, a three-judge panel of the 9th US Circuit Court of Appeals denied a request to block the broadcasts. Opponents of the recording say they fear witnesses' testimony may be affected if cameras are present.

The ruling probably will be appealed to the U.S. Supreme Court, and its ruling in the case could set precedent for whether gay marriage would become legal nationwide.

"This could be our Brown vs. Board of Education," said former Clinton White House adviser Richard Socarides, referring to the 1954 Supreme Court decision that outlawed racial segregation in US public schools. "Certainly the plaintiffs will tell you they are hoping for a broad ruling that says that any law that treats someone differently because of sexual orientation violates the US Constitution."

The case marks the first federal trial to examine whether the US Constitution allows the banning of marriages between couples of the same sex, and the challenge is being bankrolled by a group of liberal Hollywood activists led by director Rob Reiner.

They retained two of the nation's most influential lawyers to argue the case - former US Solicitor General Theodore Olson and trial lawyer David Boies. The lawyers are best known as the rivals who represented George W. Bush and Al Gore in the dispute over the 2000 presidential election in Florida, in which the justices' order ended recounts and gave the presidency to Bush.

California's Republican Gov. Arnold Schwarzenegger and Democratic Attorney General Jerry Brown are defendants in the lawsuit by virtue of their prominent positions in California government, but both opposed the ban and have refused to defend the suit in court. Schwarzenegger has taken no position on the case, while Brown filed a brief saying he agreed with the Olson-Boies team that gays have the same federal constitutional right to marry as heterosexuals.

Walker says the case is so important that the court has taken the rare step of allowing videotaping of the proceedings so the public can watch. The trial, scheduled to start today, will air on YouTube unless the blocked it overnight.

Gay marriage is legal in five states: Connecticut, Iowa, Massachusetts, New Hampshire and Vermont.