The federal judge presiding over a San Francisco trial on Proposition 8 ordered Monday that two groups supporting same-sex marriage must turn over campaign documents to the other side.
U.S. District Judge Vaughn Walker said the documents from Equality California and the American Civil Liberties Union could help show the "mix of information available to voters" when they approved Proposition 8.
He ordered the groups to turn over the documents to the official sponsors of Proposition 8 by March 31.
The initiative measure, enacted by California voters in 2008, amended the state Constitution to ban same-sex marriage.
Walker is presiding over a non-jury trial in which two same-sex couples claim the measure violates their federal constitutional rights. The sponsors of Proposition 8 are defending it in court.
Testimony in the trial was completed in a two-and-one-half-week proceeding before Walker in January. But the judge kept the trial open until the dispute over the documents was resolved.
A lawyer for the ACLU told Walker at a hearing last week that the group would appeal any order requiring it to surrender campaign documents. Such an appeal could further delay resolution of the case.
Closing arguments before Walker have not yet been scheduled.
Walker is expected to issue a written ruling at some point after hearing the final arguments. The decision can then be appealed to a federal appeals court and the U.S. Supreme Court.
The trial is the nation's first on a federal constitutional challenge to a state prohibition on same-sex marriage.
The Proposition 8 sponsors sought the campaign documents from the No on 8 groups after Walker ruled last fall that the sponsors must turn over some of their own documents.
Under the terms of a federal appeals court ruling issued in January, the documents to be turned over are those that refer to arguments for or against Proposition 8, with the exception of private, internal communications within each campaign group.
Walker's order today upheld a similar ruling issued by a federal magistrate earlier this month.