On Valentine's Day last month, about a dozen gay and lesbian couples showed up at San Francisco City Hall. They wanted something they knew they couldn't have: A marriage license.
The protest, organized by Marriage Equality USA, happens every year. And every year the couples are turned away.
Thom Watson from Daly City came with his partner.
"You're really never fully prepared for what it's going to feel like yet again to be turned down for something that you want so badly and that other people take for granted," Watson said.
The right to get that legal document from a county clerk is what Tuesday's U.S. Supreme Court hearing is all about: whether California's Proposition 8 -- a constitutional amendment defining marriage as a union of a man and a woman -- violates equal protection under the law guaranteed by the U.S. Constitution.
Supporters: What's at Stake
To the sponsors of Prop. 8, like Protect Marriage.com attorney Andrew Pugno, California voters had a good reason for limiting marriage to one man and one woman.
"We'd be in a very different world if a small minority can choose a new lifestyle,” Pugno said, “and then insist on a constitutional right to have government uphold that choice as an ideal.”
In briefs filed with the Supreme Court, Pugno's legal team argues the rationale for Prop. 8 is that marriage is the institution that links biological parents with their children.
"And if the parents are not encouraged to bind themselves together for the benefit of the children,” he said, “then ultimately it's the children that suffer.”
Opponents: What's at Stake
But don't tell that to Kris Perry. She and her partner Sandy Stier sued in federal court to have Prop. 8 overturned. Perry is the namesake of the case before the Supreme Court Tuesday – Hollingsworth v. Perry.
Perry says their children are the exact reason they want to get married.
"We've been together for more than 13 years," Perry said. "We've raised four boys. There is nothing that would make that more real and permanent than the right to be married."
Two federal courts have already ruled that preventing gay and lesbian couples from getting married serves no rational purpose and is based on prejudice.
What Could Happen
The fate of Prop. 8 may hinge on how the justices view the motivations behind banning gay marriage, according to Stanford Law School professor Jane Schacter.
"On this fundamental question – what is the government's reason for doing this – if it's no more than prejudice or animosity toward the disadvantaged group, then Prop. 8 is not going to stand," Schacter said.
If Prop. 8 is struck down, gay and lesbian couples will be able to get married in California.
But those marriages still won't be recognized by the federal government for things like filing joint taxes, Social Security benefits or inheritance taxes, unless the Supreme Court also strikes down the Defense of Marriage Act, or DOMA.
That issue will be heard Wednesday.
'Frustrated, Complicated and Galling'
And no one will be watching more carefully San Francisco resident Karen Golinski. She and her partner got married in California when it was legal -- but then she couldn't add her wife to her health plan.
"I'm tired of my life being so much harder than everybody else's," Golinski said. "I just want it to be the same. I'm not asking for special benefits or special privileges. I just want to be treated equally like all my neighbors."
Golinski is raising a 10-year-old son with her spouse Amy Cunninghis, who said the unequal treatment takes a financial and emotional toll on them.
"It is frustrating, complicated and galling to be legally married and then not have that marriage recognized by everyone," Cunninghis said.
How the Court Could Rule
The Obama Administration has weighed in on both cases, urging the Supreme Court to strike down DOMA and Prop. 8.
The court has many options when it comes to deciding Prop. 8, said UC Davis Law School Professor Vik Amar.
"It could rule very broadly in either direction,” Amar said. “It could strike down all bans on same-sex marriage. It could uphold all regulation or prohibition on same-sex marriage. Or it could rule like the 9th Circuit to do something in between."
That "something in between" would mean striking down Prop. 8 on narrow grounds that apply only in California.
Since Prop. 8 passed, support for gay marriage has gradually grown. Just this month a statewide poll found that 61 percent of California voters now support allowing gays and lesbians to marry. Fortune 500 companies and prominent Republicans have filed legal briefs opposing Prop. 8.
But will the court be influenced by shifting attitudes? Or will it just allow each state to decide for itself?
Ryan Anderson, a fellow at the conservative Heritage Foundation in Washington, D.C., frames it this way: "Will the Supreme Court allow citizens and their elected officials to make marriage policy, or will the Supreme Court cut democratic deliberations short, create another Roe v. Wade and another 40-year culture war?"
For Stier, the wait has gone on long enough.
"We have no idea when marriage will be legal in California," she said. "But what we do know is when it is legal in California, we'll be the first in line."
Stier and Perry will be in the courtroom tomorrow morning with their twin sons.
The justices will issue their rulings on both Prop. 8 and DOMA by the end of June.