Convention 15 of the Shadow Proclamation

Convention 15 of the Shadow Proclamation was a subsection of the Shadow Proclamation. It dealt with the cessation of hostile actions in order to parley. (NSA: Peacemaker)

The Ninth Doctor used it to seek audience with the Nestene Consciousness. (DW: Rose)

Rose Tyler tried to invoke Article 15 along with other aliens, places, and things she had encountered in her travels with the Ninth Doctor to try to convince the Sycorax to leave Earth alone. They merely laughed at her. (DW: The Christmas Invasion)

Rose's reference to Article 15 rather than Convention 15 was presumably an error on her part.

The Tenth Doctor yet again used this phrase against the Isolus, but it did not care. (DW: Fear Her) He used it successfully to communicate with the Clade. (NSA: Peacemaker)