Brown filed a brief Thursday asking the court to deny a preliminary injunction sought by supporters of Proposition 8. If granted, the injunction would free them from having to file campaign finance reports detailing late contributions.
The measure's supporters also have asked the court to order state officials to remove names of donors that already have been posted on the secretary of state's Web site.
The supporters contend that revealing donor names has led to harassment of some contributors.
Brown says the proposition's supporters do not qualify for an exemption to contribution disclosure laws that the U.S. Supreme Court carved out for persecuted minorities.
Oral arguments in the case are scheduled for Jan. 29.