San Francisco- California’s Supreme Court will hear arguments Tuesday on whether San Francisco’s mayor abused his municipal powers when he issued thousands of marriage licenses to same-sex couples this year.

The arguments will focus on how much leeway elected officials have to interpret the law, and experts predict Mayor Gavin Newsom will lose. California law clearly defines marriage as a union between a man and woman. In 2000, voters also approved a statewide initiative requiring the state to only recognize marriage between opposite sexes.

A Christian legal advocacy group will be part of the case against Newsom.

Alliance Defense Fund lawyer Jordan Lorence will maintain that Newsom cannot unilaterally decide that the state’s marriage law is unconstitutional.

The Alliance Defense Fund’s chief counsel, Benjamin Bull, said, “Our starting point is the Bible, always … but we understand we operate in a secular judicial system where you need to develop winning arguments and strategies that will be accepted by secular judges.”

Until a lawsuit by gay couples denied licenses reaches the court in a couple of years, the marriages performed in San Francisco are largely symbolic.

California Attorney General Bill Lockyer and gay marriage opponents are urging the court to take the next step and invalidate them.

The marriage licenses in San Francisco followed a ruling in Massachusetts that the state could not deny marriage to same-sex couples. That was the start of a flurry of activities that included President George W. Bush calling for a constitutional amendment defining marriage as between a man and a woman, and similar activities in many states.

Earlier this month, Massachusetts began marrying same-sex couples, though an amendment that could pass as early as 2006 could end the practice in that state.