The American Civil Liberties Union and Equality California, two of the groups that must turn over the campaign materials, said Monday they are reviewing Walker's order to determine whether to appeal it.

The ACLU and Equality California, the state's largest gay rights group, had argued that the campaign documents being sought were irrelevant to the Proposition 8 lawsuit. They also claimed it was unfair to make them bear the expense of sifting through tens of thousands of old e-mails.

"We do believe this decision is incorrrect," said Geoffrey Kors, Equality California's executive director. "A core issue in the case is whether the motivation of those who put Prop. 8 on the ballot is animus (dislike for gays). Why people opposed Prop. 8 is not relevant."