Lawyers for an open government group told the Indiana Supreme Court that lawmakers should be required to comply with the state's public records act.
An attorney for the Citizens Action Coalition said Thursday that lawmakers should disclose their emails, especially if the messages deal with campaigning or fundraising.
The group is appealing an August ruling by a Marion County judge who said he could not interfere in legislative branch operations.
The Citizens Action Coalition had requested the emails of Republican state Rep. Eric Koch of Bedford and the House GOP caucus, but was turned down. Koch sponsored an unsuccessful bill last year that would have cut how much utilities must pay for excess electricity generated by home solar power systems.
Legislative leaders say they are exempt from public records law.
This story will be updated.