The Lex Imperialis, also called the Dictates Imperialis, is the legal code of the Imperium. Claimed to be the word of the Emperor himself, it is a vast body of laws and codes compiled over ten thousand years that Judges of the Adeptus Arbites spend their entire lives studying and compiling in the Book of Judgement. Though each world of the Imperium has its own unique set of rules, the Lex Imperialis is the definitive and absolute word, ruling above all others. The Lex Imperialis is ruthlessly enforced by the Adeptus Arbites.
While the Dicatates Imperialis are extensive, the huge volume of prior cases and sometimes contradictory rulings can make it difficult to determine the correct decision. In especially complex cases, it may take centuries to reach an outcome. A Judge may spend his entire life deliberating, scrutinizing, and trying to fathom out the issues, only to pass his work on, unfinished, for others to continue. Millennia later, though the accused are long dead, a ruling is finally made and justice must be meted out upon the distant descendants and those obscurely associated with the original transgressor.