California's voter-approved Proposition 8, which effectively bans gay marriage in the state, heads to a federal appeals court in San Francisco Monday.
No matter the outcome, the case is expected to end up before the U.S. Supreme Court.
The hearing will consider whether Proposition 8 - definining marriage as between one woman and one man - is constitutional.
Seven million Californians voted for the law two years ago, but outgoing Republican Gov. Arnold Schwarzenegger and state Attorney Gen. Edmund G. Brown, Jr. have refused to defend it.
In fact, Imperial County is the only legal jurisdiction in the Golden State that has enforced the measure. The appeals court will decide whether the county and its lawyers have the legal standing to enforce it.
Earlier this year U.S. District Judge Vaughn Walker ruled the law was not constitutional. Now, a panel of three judges from the 9th Circuit Court of Appeals will hear and decide.
Prop 8 defenders had requested that one of the judges, Judge Stephen Reinhardt, recuse himself from the case. Reinhardt's wife heads the American Civil Liberties Union in Southern California and has publicly opposed the law. However, late last week, the judge denied their request.
For now, the only thing that both sides of the issue can agree upon is its national implications. CBN News spoke with attorney Jordan Lorence, who has helped advise Prop 8 defenders.
"This Proposition 8 case is bigger than California and bigger than the definition of marriage," Lorence said. "It not only affects the definition of marriage but also religious liberty and freedom of conscience."
Monday's hearing is scheduled to last a few hours. But legal observers said the judges could take up to a year before reaching a decision in the case.