(written from a Production point of view)
According to the script of Star Trek IV: The Voyage Home , Argus was a party involved in a peace pact with Rigel IV, sometime prior to stardate 8390. It may correspond to one of several places named Argus.
In the pages of that pact, a significant legal precedence was laid down. According to this pact, All beings may not be created equal yet shall be given equal opportunity and treatment under the law. Sometime later, a recovering Spock was asked during a memory testing session to state this precedence.