A California judge has ordered opponents of Proposition 8, the voter approved initiative defining marriage as being between one man and one woman, to surrender their internal campaign emails and memos.
U.S. District Judge Vaughn Walker said sponsors of Prop 8 were entitled to the information in the defense against a lawsuit challenging the measure.
Meanwhile, the American Civil Liberties Union and Equality California - two of the groups impacted by the ruling - say they plan to appeal the decision.
"We do believe this decision is incorrect," said Geoffrey Kors, executive director of Equality California, the state's largest gay rights group.
"A core issue in the case is whether the motivation of those who put Prop. 8 on the ballot is animus (dislike for gays)," he argued. "Why people opposed Prop. 8 is not relevant."
Monday's ruling could delay a verdict in the trial.
The Prop 8 trial is the first case in federal court to see if the U.S. Constitution prevents states from outlawing gay marriages.