The Azura Codex was for a long time the reigning law book of the entire Citadel, written up by the former Azure Arché Kallistrata the Just.
Before the fall of the Rex Arché title, it was the main scripture to which you turned for justice. Nowadays, most Towers are attemtping to organize their own law-system in the wake of the War of Suites, but the Azura Codex remains extremely influential in the writing of other Towers' law.
The Azura Codex is old, and has met some opposition in the Azure Tower for being too archaic and harsh. All this aside, it's still frequently quoted in Azurite halls as a way to win an argument, and the Azure Inquisition follow it down to the letter.