May be found during a random encounter in which three Morag Tong Assassins attack the Dragonborn, which usually occurs during the quest "Served Cold." This random encounter is only possible if the Dragonborn is a member of the Dark Brotherhood, the Morag Tong's sworn enemy.
Honorable Writ of Execution: <player's name>
The aforementioned personage has been marked for execution as a member of an unlawful guild of assassins in accordance with the lawful tradition and practice of the Morag Tong Guild. The Bearer of this non-disputable document has official sanctioned license to kill the afore-mentioned personage.