Article 7

Article 7 of Gallifreyan law prohibited Time Lords from committing any form of genocide. While the Sixth Doctor was on trial for interfering in the affairs of other peoples and planets, the Valeyard accused him of genocide for destroying the Vervoids aboard the Hyperion III. (TV: Terror of the Vervoids)

In a parallel universe, article seven of Gallifreyan law forbade state-authorised genocide. It dated back to the Vampire Wars and was countersigned by Rassilon himself. (PROSE: The Quantum Archangel)
 * How much of this corresponds to the prime universe is unclear.