The U.S. Supreme Court by a 5-4 vote today blocked the broadcasting of a federal trial in San Francisco on the constitutionality of California’s ban on same-sex marriage.

The trial began Monday before U.S. District Judge Vaughn Walker and is the first federal trial in the nation on a U.S. constitutional challenge to same-sex marriage limits.

California’s ban was enacted by voters in 2008 as Proposition 8.

The broadcasting authorized by Walker last week would have included a live video feed to five other federal courthouses and a delayed Internet broadcast on a government channel on YouTube.

It would have been the first televising of a federal trial in western states, under a pilot program announced by the 9th U.S. Circuit Court of Appeals in December.

But the high court majority, ruling in an emergency appeal filed by the sponsors of Proposition 8, said the district court failed to provide enough time for public notice and comment on the broadcasting.

The majority said in a 17-page ruling that the trial court “attempted to change its rules at the 11th hour” in a way that “could compromise the orderly, decorous, rational traditions that courts rely upon.”

The panel granted an indefinite stay that continues a temporary stay it issued Monday one hour before the trial began.

The stay will remain in effect until the Proposition 8 sponsors file a full appeal of Walker’s order and receive a ruling–a process that normally would not be completed until long after the two-week trial is completed.

The stay applies to the plan to allow the live video feed to the five other federal courthouses at the 9th Circuit in San Francisco and in Pasadena, Seattle, Portland, Ore., and Brooklyn, N.Y.

The related plan to allow delayed broadcast on YouTube was not before the court because it had not yet been approved by 9th Circuit Chief Judge Alex Kozinski. But the court majority’s reasoning for granting the stay would apply to the YouTube plan as well.

In addition to citing inadequate public notice, the majority said Proposition 8 sponsors showed they could be harmed by broadcasting because of alleged potential intimidation and harassment of witnesses.

It also said that because the high-profile trial concerns a contentious issue, “This case is therefore not a good one for a pilot program.”

The five judges in the majority were Chief Justice John Roberts and Justices Antonin Scalia, Clarence Thomas, Anthony Kennedy and Samuel Alito. The decision was a “by-the-court” ruling that did not indicate the author.

Justice Stephen Breyer wrote in a 10-page dissent that there was adequate public notice, that there was no evidence of harm to witnesses and that the majority was seeking to “micromanage” local court rules.

Breyer, joined by Justices John Paul Stephens, Ruth Bader Ginsburg and Sonia Sotomayor, said, “The public interest weighs in favor of providing access.”

Thomas Burke, a lawyer representing 12 media organizations that urged the courts to allow broadcasting, said, “It’s obviously disappointing. This was an extraordinary opportunity to let the public know what is happening in this case.”

Burke said, “It’s obvious to me that a nerve has been struck on the court, for the entire court to issue a 5-4 decision.

“The entire court believes this is an extraordinary event taking place in San Francisco,” Burke said.

A spokesman for Proposition 8’s sponsors and their campaign committee,, was not available for comment.

Rick Jacobs, chair of the pro-gay-marriage Courage Campaign Institute, said, “The Supreme Court just struck a huge blow against transparency and accountability.”

Geoff Kors, executive director of Equality California, said, “We are deeply disappointed with the high court’s ruling.”

Meanwhile, the trial continued today in Walker’s Federal Building courtroom with testimony from two expert witnesses on behalf of the two same-sex couples who filed the lawsuit in May.

George Chauncey, a Yale University history professor, testified that television advertisements used by Proposition 8 supporters in the 2008 ballot campaign reflected arguments used to oppose gay rights for the past several decades.

The advertisements “draw on a long history of hostility and stereotypes and fear,” he told Walker.

Chauncey was followed to the stand by Letitia Peplau, a psychology professor at the University of California at Los Angeles, who testified about the effects of marriage on individuals’ health and well-being.

Thursday’s witnesses will include the chief economist of the city of San Francisco, a Columbia University professor and author Helen Zia.

The lawsuit plaintiffs, Kristin Perry and Sandra Stier of Berkeley and Paul Katami and Jeff Zarrillo of Burbank, contend that Proposition 8 violates their federal constitutional rights to due process and equal treatment.

Walker will decide the case without a jury.

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