The term "The Scales of Injustice" is not widely recognized as an established concept, legal doctrine, historical artifact, or distinct philosophical framework in general reference works. It does not possess a standard encyclopedic definition independent of specific creative works.
The phrase appears most prominently as the title of a 2003 Doctor Who novel by Gary Russell (part of the Past Doctor Adventures series). It may also be used as a rhetorical variation of the common symbol "Scales of Justice" to imply systemic bias, corruption, or the failure of legal systems, but this usage is descriptive or metaphorical rather than a proper noun denoting a specific entity.