On the 17th floor of the Phillip Burton Federal Building in a city known for being at the edge of social change, a federal trial is under way that could lead to a landmark ruling on same-sex marriage in America.

Perry v. Schwarzenegger, which began Jan. 11 in the US District Court for Northern California, challenges the constitutionality of California's voter-approved ban on gay marriage. Over the past 10 days, lawyers have made a broad-based case against Proposition 8, ranging from arguments that it reflects prejudice against gays and lesbians to discussions about the nature of modern marriage, and the notion that homosexuality requires special protections like gender and race.

Many gay-marriage advocates say the case is ultimately destined for the US Supreme Court and represents the best path to legalizing same-sex marriage. They hope this lawsuit will be their Loving v. Virginia – the 1967 case that ended race-based restrictions on marriage.

But not all activists are on board. Some worry the stakes are too high: a federal challenge at a time when most states and voters reject gay marriage could be premature. Even if the Supreme Court eventually takes the case – bound to be appealed by the losing side in San Francisco in the Ninth Circuit Court of Appeals and then to the Supreme Court– the court has historically been reluctant to move too far ahead of the people. A defeat in the Supreme Court would deal a huge setback to a movement that has seen significant gains over the past decade.

"The national marriage project was assiduously avoiding a federal court challenge. They were working slowly toward [it]," says Marc Spindelman, a law professor at Ohio State University and an expert on gay and lesbian rights. But, he adds, "if there's a circuit court that's likely to recognize same-sex marriage" it's the Ninth Circuit, under which the district court falls and which is often branded the most liberal.

A divided U.S. Supreme Court struck down decades-old restrictions on corporate campaign spending, reversing two of its precedents and freeing companies to conduct advertising campaigns that explicitly try to sway voters.

The 5-4 majority, invoking the Constitution's free-speech clause, said the government lacks a legitimate basis to restrict independent campaign expenditures by companies. The ruling went well beyond the circumstances in the case before the justices, a dispute over a documentary film attacking then-presidential candidate Hillary Clinton.

"When government seeks to use its full power, including the criminal law, to command where a person may get his or her information or what distrusted source he or she may not hear, it uses censorship to control thought," Justice Anthony Kennedy wrote for the majority. "This is unlawful. The First Amendment confirms the freedom to think for ourselves."

Companies, which had been barred since 1947 from using general-treasury dollars in support of or in opposition to a candidate, now can spend millions of dollars on their own campaign ads, potentially punishing or rewarding lawmakers for their votes on legislation. Labor unions, though they weren't directly at issue in the case, have been subject to the same restrictions and may also now expand their political spending.