Here is a look at the background of the Prop 8 case, Hollingsworth v. Perry (as outlined spectacularly by gay-focused site Data Lounge).
What is this whole Prop 8 thing? In 2008, just months after the California supreme court endorsed same-sex marriage, the state’s voters amended the state constitution to repudiate the ruling and ban such unions. Two prominent lawyers, Theodore B. Olson and David Boies, challenged the ban as a violation of the federal Constitution on behalf of two same-sex couples.
In an interesting twist, the lawyers are ideological opposites who faced off in Bush v. Gore, the Supreme Court case in late 2000 that delivered the presidency to George W. Bush. Some gay rights activists worried that their legal strategy in this case was too aggressive.
After a trial, a judge in San Francisco struck down Proposition 8 in a broad ruling whose logic would apply to bans around the nation. California officials did not appeal the ruling against them.
The United States Court of Appeals for the Ninth Circuit, in San Francisco, ruled that proponents of Proposition 8 had standing to appeal the judgment against the state. The court then affirmed the trial judge’s decision but on a narrower ground, saying voters were not entitled to withdraw a constitutional right once it had been established by the state supreme court.
The reasoning of the appeals court decision, calculated to appeal to Justice Anthony M. Kennedy, would not directly threaten bans in other states.