TV3 has been found guilty of breaching broadcasting laws for playing advertising during some Rugby World Cup games.
The screenings during the 2007 event were on Sunday mornings, when advertising is banned.
TV3's parent company Mediaworks now faces fines of up to $300,000 on the three charges.
Ministry of Arts Culture and Heritage pressed the charges.
The ministry's broadcasting unit director Jo Tyndall, says the ministry has a duty to uphold the law. She told Morning Report sentencing has yet to be determined.