Olson said in an interview before the court acted that he would make California-specific arguments as well as broader contentions that could establish same-sex marriage rights nationwide. Marriage, Olson said, is a "fundamental right that cannot be taken away from citizens on the basis of their sex or sexual orientation."
In court papers, Olson and Boies defended Reinhardt's reasoning. They said the judge correctly concluded that, by stripping away marriage rights, Proposition 8 "achieves nothing except the marginalization of gay and lesbian individuals and their relationships."
Gay marriage is on hold in California while the litigation plays out. More than 18,000 same-sex couples were married in the state before the ballot initiative passed.
Both sides asked the court to take up DOMA, a law the Obama administration decided last year it would begin opposing in court. That reversal left it to congressional Republicans led by House Speaker John Boehner to spearhead the defense.
Opponents say the law violates the Constitution's equal protection guarantee by denying legally married gay couples the same federal benefits as opposite-sex spouses. Under the law, people in same-sex marriages can't file joint federal tax returns, claim exemption from estate taxes, receive Social Security survivor benefits or obtain health insurance as the spouse of a federal employee.
Supporters of the law say it promotes traditional marriage, and by extension makes it more likely that children will grow up in a nurturing environment.
"Traditional marriage protects civil society by encouraging couples to remain together to rear the children they conceive," 15 states led by Indiana argued in court papers. "It creates the norm that potentially procreative sexual activity should occur in a long-term, cohabitative relationship."
The Boston-based 1st U.S. Circuit Court of Appeals and the New York-based 2nd Circuit rejected that reasoning. Ruling in the Massachusetts case, the 1st Circuit pointed to "a lack of any demonstrated connection between DOMA's treatment of same-sex couples and its asserted goal of strengthening the bonds and benefits to society of heterosexual marriage."