Jabba warns Han Solo:
Jabba: Okay, 15%. But if you fail me again...I'll put a price on your head so big... you won't be able to go near a civilized system.
What does "civilized system" mean in Star Wars universe?
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He was possibly referring to the Convention of Civilized Systems, something similar to the Bill Of Rights that determined a species sentience. It was referred during the Clone Wars series in Season 1 Episode 15.
It is obvious these creatures are not covered by the Convention of Civilized Systems. The Jedi Council has no say in the matter." ―Chairman Chi Cho, on the Talz
Although that might be the in-universe explanation, I believe that the real world explanation is the exact opposite, they took Jabba's words and built on top of it.