The sanctified rules of combat, or ancient rites of combat, were followed by the Sycorax.
On 25 December 2006, the Tenth Doctor, noting that the "sanctified rules of combat" still applied, stood as the champion of the planet Earth, which the Sycorax had invaded, as he challenged the Sycorax leader Fadros Pallujikaa to a sword duel atop the Sycorax spaceship for the planet. To that end, the Doctor warned Rose Tyler against interfering, as to do so would invalidate the challenge and hand the win to the Sycorax. Ultimately, the Doctor defeated the Sycorax leader in combat but chose to spare his life after imparting a "champion's command", making the Sycorax swear on the blood of his species that he would leave the Earth and never return. Though he ostensibly accepted, the Sycorax leader attempted to attack the Doctor as soon as his back was turned only to be outwitted by the Time Lord, who hit a switch which sent the Sycorax falling to his death. Following the duel, the Doctor, standing within the Sycorax ship, forbade the Sycorax from scavenging on Earth "for the rest of time" by the "ancient rites of combat". (TV: The Christmas Invasion)