The US Supreme Court has blocked efforts to have a historic gay-marriage trial broadcast in real time on YouTube.

The decision reveals an emerging pattern by the nation's highest court to protect the identities of gay rights opponents on the grounds that they could be harmed or threatened with violence if their names were publicly released.

US District Court Judge Vaughn Walker last week allowed the proceedings in a case that opens today to be videotaped, at the urging of opponents of Proposition 8, California's constitutional amendment banning gay marriage. Gay-rights advocates argued that having the case open to the public was important because of the intense interest in the case nationwide. But lawyers for Proposition 8's defenders argued that having the case broadcast would cause harm to their clients by potentially exposing them to public anger.

On Monday, the Supreme Court agreed with the Prop 8 defenders, granting them a temporary injunction to prevent mass broadcast of the proceedings, allowing the broadcast only inside other parts of the courtroom. The injunction is valid only until Wednesday, Jan. 13.

As the L.A. Times notes, this is the second time in recent months that "the high court has intervened on behalf of the defenders of 'traditional marriage' and granted an emergency appeal."

In October, the justices blocked officials in the state of Washington from releasing the names of 138,000 people who signed ballot petitions seeking to overturn a state law giving equal benefits to gay and lesbian couples. Under Washington law, the names were considered public record. But attorney James Bopp told the high court that the signers of these petitions could be subjected to harassment if their names were revealed. And the court granted an order blocking the release.

Justice Stephen Breyer was reportedly the only dissenting voice in the decision. "In my view, the court's standard for granting a stay is not met," Breyer wrote. "In particular, the papers filed, in my view, do not show a likelihood of 'irreparable harm.' "

The case, known as Perry v. Schwarzenegger, is being watched closely by both gay-rights activists and opponents of gay marriage because it marks the first time that a state ban on gay marriage is being challenged on the grounds that it is unconstitutional under the federal constitution. In all likelihood, the case will end up with the Supreme Court, where issues of states' rights will inevitably come in to play.

One of the more remarkable elements of Perry v. Schwarzenegger is that the two lawyers arguing against Proposition 8 -- David Boies and Ted Olson -- were on opposite sides of Bush v. Gore, the 2000 Supreme Court case that ended with the Supreme Court putting an end to Florida ballot recounts, resulting in George W. Bush becoming president.

Olson, who argued the Bush side in that case, is a noted conservative and his support for gay marriage has raised some eyebrows in the conservative community. In an comment piece published last week in Newsweek, Olson argued that conservative opposition to same-sex marriage "does not make sense."

Many of my fellow conservatives have an almost knee-jerk hostility toward gay marriage. This does not make sense, because same-sex unions promote the values conservatives prize. Marriage is one of the basic building blocks of our neighborhoods and our nation. ... The fact that individuals who happen to be gay want to share in this vital social institution is evidence that conservative ideals enjoy widespread acceptance. Conservatives should celebrate this, rather than lament it.

Legalizing same-sex marriage would also be a recognition of basic American principles, and would represent the culmination of our nation's commitment to equal rights. It is, some have said, the last major civil-rights milestone yet to be surpassed in our two-century struggle to attain the goals we set for this nation at its formation.

Olson's participation is particularly significant, says Jennifer Pfizer of gay-rights legal advocacy group Lambda, because of his past as a Republican lawyer. "His advocacy and passion for equal treatment of lesbian and gay couples here will reach the ears and hearts of many people who have not understood this issue before," she said.

In 2008, the California state supreme court ordered the state to issue marriage licenses to same-sex couples, arguing the prohibition on gay marriage was unconstitutional. Opponents of gay marriage responded with a ballot initiative amending the state constitution to ban gay marriage. That initiative passed in the 2008 election, with 52 percent of voters in support.

Judge Vaughn Walker's decision to hear the challenge to Prop 8, on the grounds that it's unconstitutional under the US Constitution, has angered those against gay marriage, who argue that Californians have already spoken on the issue.

"This lawsuit is an attempt by Judge Walker to put the voters of California on trial, and it's wrong. Walker has not dealt with this properly. He doesn't care about the law," Brian Brown, director of the National Organization for Marriage, which opposes gay marriage, told AFP.

"I think our founding fathers would be rolling over in their graves if they heard that the constitution guarantees the right to redefine marriage. This is absurd," he said.

-- With Agence France-Presse