LOS ANGELES -- After a run of setbacks at the state level, gay rights advocates will take the campaign for same-sex marriage into a federal courtroom on Monday, starting down a treacherous avenue that ends at a U.S. Supreme Court dominated by conservatives.

Opponents frame the case as a challenge to the people's right to make law. In every one of the 31 state ballots where the issue has appeared, voters have defeated it, most recently in Maine. In the five states that permit such unions -- the District will join them this year -- the change came by legislation or court decision.