Gay-marriage proponents filed three court challenges Wednesday against the new ban. The lawsuits raise a rare legal argument: that the ballot measure was actually a dramatic revision of the California Constitution rather than a simple amendment. A constitutional revision must first pass the Legislature before going to the voters.

"Where do you draw the line between 'revision' and 'an amendment' when those are words in conversation we would use interchangeably?" asked Erwin Chemerinsky, dean of the University of California, Irvine law school. "It's a highly technical legal question in a highly charged political atmosphere."

Andrew Pugno, attorney for the coalition of religious and social conservative groups that sponsored the amendment, called the lawsuits "frivolous and regrettable."

"It is time that the opponents of traditional marriage respect the voters' decision," he said.

The high court has not said when it will act. State officials said the ban on gay marriage took effect the morning after the election.

"We don't consider it a 'Hail Mary' at all," said Kate Kendell, a Utah native and executive director of the National Center for Lesbian Rights. "You simply can't so something like this — take away a fundamental right at the ballot."

With many gay newlyweds worried about what the amendment does to their vows, California Attorney General Jerry Brown said he believes those marriages are still valid. But he is also preparing to defend that position in court.

"I wish I could be comforted by Attorney General Brown's statement that it has no retroactivity," said Loyola Law School professor Bill Araiza, who married his same-sex partner Oct. 29. "But it's in flux and I just don't know."

The amendment does not explicitly say whether it applies to those already married. Legal experts said unless there is explicit language, laws are not normally applied retroactively.

"Otherwise a Pandora's Box of chaos is opened," said Stanford University law school professor Jane Schacter. Still, Schacter cautioned that the question of retroactivity "is not a slam dunk."

An employer, for instance, could deny medical benefits to an employee's same-sex spouse. The worker could then sue the employer, giving rise to a case that could determine the validity of the 18,000 marriages.

Supporters of the ban said they will not seek to invalidate the marriages already performed and will leave any legal challenges to others.

A 2003 California law already gives gays registered as domestic partners nearly all the state rights and responsibilities of married couples when it comes to such things as taxes, estate planning and medical decisions. That law is still in effect.