**The first US federal trial to determine whether states are allowed to ban same-sex marriages has begun in San Francisco, California.**Any ruling reached is expected to be challenged, possibly taking the case all the way to the US Supreme Court.
A Supreme Court ruling would determine the fate of gay marriages nationwide, without the possibility of appeal.
The suit, filed by two gay couples, challenges Proposition 8 - a ban on gay marriage in the state of California.
The law amended California’s constitution to restrict marriage to a union between a man and a woman.
'Media circus’
The case has not only pitted opponents and defenders of Proposition 8 against each other, it has also kicked off a debate about the pros and cons of broadcasting the proceedings.
CALIFORNIA GAY MARRIAGE
- 2004 San Francisco begins issuing marriage licences to same-sex couples - a move annulled by Supreme Court months later
- May 2008 Supreme Court votes 4-3 to legalise same-sex marriage; introduced in June
- November 2008 Voters approve Proposition 8 limiting marriage to heterosexual couples
- **March 2009 ** Civil-rights lawyers argue before Supreme Court that referendum is anti-constitutional
- May 2009 Supreme Court rules Proposition 8 is constitutional
Less than two hours before the trial was started, the Supreme Court temporarily blocked a plan to post video of the proceeding on the internet site YouTube.
The Supreme Court complied with an emergency request by lawyers who had argued that broadcasting the trial would turn it into a media circus.
The court has blocked the broadcast until Wednesday afternoon to allow for further consideration of the arguments brought by both sides.
Chief US District Judge Vaughn Walker had agreed to the taping after a recent rule change allowed for televised coverage of some civil cases.
He said the case was appropriate for wide dissemination because it dealt with an issue of wide interest and importance.
Court showdown
Backers of Proposition 8 say the federal case starting in San Francisco is the latest attempt to overturn what they say is the will of the people as expressed by the 52% who backed the amendment in a 2008 referendum.
Judge Vaughn Walker will have to decide whether the ban on same-sex marriage in California is constitutional.
The case, which has been brought by two gay couples, will see high-profile lawyers Theodore Olson and David Boies argue that Proposition 8 denies gays the fundamental right to marry.
Supporters of Proposition 8 will argue California does not discriminate against gays, as the current law allows them to get married - as long as they wed a partner of the opposite sex.