The Ninth Circuit court is considered to be one of the most liberal courts in the country, but the three judges that will hear the case are chosen at random and can span the ideological spectrum, so the fate of Prop 8 remains unclear.
The state of California is the official defendant, but refuses to act.
"The court may have to decide whether the "Yes on 8" interveners have standing to appeal, and if they don't the decision at the district court level will be final," San Francisco Deputy City Attorney Therese Stewart said.
Also still unresolved is whether same-sex marriages should resume during the appeals process.
Both sides have until Friday to file their written arguments.
USC law professor David Cruz, a constitutional and gender law specialist, thinks Judge Vaughn Walker will allow marriages to proceed because he clearly did not want the discrimination to continue.
"He's inclined to look at this and say a stay isn't protecting anyone because there's no harm if we let same-sex couples start getting married, so he might not be disposed to granting the defendant's request," Cruz said.
Some businesses in San Francisco's Castro district hope Cruz is right. The recession has been tough on them and they could use a boost.
Designers at Ixia Flower Shop say their new boutonnieres would be perfect for upcoming nuptials.
"During the time the weddings were legal, there was a ton of business for weddings for same-sex couples," shop owner Gary Weiss said.
But most legal analysts believe Walker is unlikely to allow the same-sex marriages to resume because of the mess it would create, similar to what happened in San Francisco when the city started marrying gay couples, only to have the marriages be overturned by a court later.
"He didn't want to add to the confusion, he didn't want to create yet another class of people who rely on a decision and enter into marriage and who might years down the road have those marriages taken away by the Supreme Court," ABC7 legal analyst Dean Johnson said.
Looking Back At Prop 8
Couples celebrate Prop 8 ruling at SF City Hall Castro District celebrates Prop 8 ruling PHOTOS: California reaction to Prop 8 ruling Judge rules Prop 8 unconstitutional Future of Proposition 8 now in hands of judge
PHOTOS: Final day of Prop 8 trial
Prop 8 trial re-enacted on the web
Defense lawyers rest case at Prop 8 trial
PHOTOS: Same-sex marriage on trial in SF
Defense presents first witness in Prop 8 case
SF economist says gay marriage ban costs city
Prop 8 attorneys talk history of marriage
Groundbreaking same-sex marriage trial starts in SF
Judge refuses to dismiss Prop 8 suit
San Francisco joins federal battle over Prop 8
Governor wants speedy Prop 8 resolution
Prop 8 fight may head to U.S. Supreme Court
Couples challenge Prop 8 with lawsuit
PHOTOS: Prop 8 upheld in California
Castro District reacts to Prop 8 ruling
Calif. high court upholds gay marriage ban
Hundreds pray on eve of Prop 8 ruling
Justices hear Proposition 8 arguments
Mormon churches role in Prop 8 investigated
Court agrees to hear Prop 8 challenges
California remains conflicted about Prop 8
Prop 8 constitutionality challenged
No on 8 campaign concedes defeat
Same-sex couples scramble to get married
Proposition 8 campaigning begins